commit 0360e7dfccd0cd48514e4e66626f524b01767faa
Author: jslightham <johnathon@jslightham.com>
Date:   Sun May 21 23:28:11 2023 -0400

    Initial commit

diff --git a/P1/Calculator.cpp b/P1/Calculator.cpp
new file mode 100644
index 0000000..23f9c75
--- /dev/null
+++ b/P1/Calculator.cpp
@@ -0,0 +1,62 @@
+#include "Calculator.h"
+#include "VariableNode.h"
+
+using namespace std;
+
+Calculator::Calculator(int cap)
+{
+    this->data = new VariableLinkedList(cap);
+}
+
+Calculator::~Calculator()
+{
+    delete this->data;
+}
+
+/// @brief Define a new variable
+/// @param name The name of the new variable
+/// @param value The initial value to store in the variable
+/// @return True if the variable was added, false otherwise
+bool Calculator::define(string name, double value)
+{
+    return this->data->insert(name, value);
+}
+
+/// @brief Perform an operation on two variables, and store the result in a thrid
+/// @param v1 The first variable to perform the operation on
+/// @param v2 The second variable to perform the opetation on
+/// @param v3 The variable to store the output result in
+/// @param operation A lambda function to apply on the two variables
+/// @return True if successful, false otherwise
+bool Calculator::performOperation(string v1, string v2, string out, function<double(double, double)> operation)
+{
+    VariableNode *vn1 = this->data->search(v1);
+    VariableNode *vn2 = this->data->search(v2);
+    VariableNode *output = this->data->search(out);
+
+    // If a single one of the variables is not found, we cannot continue.
+    if (vn1 == nullptr || vn2 == nullptr || output == nullptr)
+        return false;
+
+    output->setValue(operation(vn1->getValue(), vn2->getValue()));
+    return true;
+}
+
+/// @brief Remove the given variable from storage
+/// @param name The name of the variable to remove
+/// @return True if the variable was successfully removed, false otherwise
+bool Calculator::remove(string name)
+{
+    return this->data->remove(name);
+}
+
+/// @brief Print out the value of the given variable
+/// @param name The name of the variable to print out
+void Calculator::print(string name)
+{
+    VariableNode *temp = this->data->search(name);
+    if (temp == nullptr)
+        cout << "variable " << name << " not found" << endl;
+    else
+        cout << temp->getValue() << endl;
+}
diff --git a/P1/Calculator.h b/P1/Calculator.h
new file mode 100644
index 0000000..b002a7b
--- /dev/null
+++ b/P1/Calculator.h
@@ -0,0 +1,22 @@
+#ifndef CALCULATOR_H
+#define CALCULATOR_H
+
+#include <iostream>
+#include <functional>
+#include "VariableNode.h"
+#include "VariableLinkedList.h"
+
+class Calculator
+{
+public:
+    bool define(std::string name, double value);
+    bool performOperation(std::string v1, std::string v2, std::string output, std::function<double(double, double)> operation);
+    bool remove(std::string name);
+    void print(std::string name);
+    Calculator(int cap);
+    ~Calculator();
+
+private:
+    VariableLinkedList *data;
+};
+#endif
diff --git a/P1/Makefile b/P1/Makefile
new file mode 100644
index 0000000..b2f8fef
--- /dev/null
+++ b/P1/Makefile
@@ -0,0 +1,2 @@
+all: test.cpp Calculator.cpp VariableNode.cpp VariableLinkedList.cpp
+	g++ -std=c++11 test.cpp Calculator.cpp VariableNode.cpp VariableLinkedList.cpp
\ No newline at end of file
diff --git a/P1/VariableLinkedList.cpp b/P1/VariableLinkedList.cpp
new file mode 100644
index 0000000..6b3a31c
--- /dev/null
+++ b/P1/VariableLinkedList.cpp
@@ -0,0 +1,88 @@
+#include "VariableLinkedList.h"
+
+using namespace std;
+
+VariableLinkedList::VariableLinkedList(int cap)
+{
+    this->maxCount = cap;
+    this->count = 0;
+    this->head = nullptr;
+}
+
+VariableLinkedList::~VariableLinkedList()
+{
+    if (head != nullptr)
+        head->DestroyAll();
+}
+
+/// @brief Insert a variable into the head of the linked list
+/// @param name The name of the variable to insert
+/// @param value The double value to initialize the variable with
+/// @return True if the variable was added, false otherwise
+bool VariableLinkedList::insert(string name, double value)
+{
+    // Ensure there is space
+    if (count == maxCount)
+        return false;
+
+    // Ensure the variable does not exist
+    VariableNode *s = this->search(name);
+    if (s != nullptr)
+        return false;
+
+    // Insert a new VariableNode into the head.
+    head = new VariableNode(name, value, head);
+    
+    count++;
+    return true;
+}
+
+/// @brief Remove the variable with name from the linked list
+/// @param name The name of the variable to remove
+/// @return True if removed, false otherwise
+bool VariableLinkedList::remove(string name)
+{
+    // Root node must be handled in a seperate case
+    if (head != nullptr && head->getName() == name)
+    {
+        VariableNode *temp = head->getNext();
+        delete head;
+        head = temp;
+        count --;
+        return true;
+    }
+
+    // Search for the node before the one we want to remove.
+    VariableNode *currentIndex = this->head;
+    while (currentIndex != nullptr && currentIndex->getNext() != nullptr && 
+           currentIndex->getNext()->getName() != name)
+        currentIndex = currentIndex->getNext();
+
+    // currentIndex will be null if the index does not exist.
+    if (currentIndex == nullptr || currentIndex->getNext() == nullptr)
+        return false;
+
+    VariableNode *temp = currentIndex->getNext()->getNext();
+    delete currentIndex->getNext();
+    count--;
+    currentIndex->setNext(temp);
+    return true;
+}
+
+/// @brief Search for the variable with the given name
+/// @param name The name of the variable to search for
+/// @return A pointer to a valid VariableNode if the node exists, nullptr otherwise
+VariableNode *VariableLinkedList::search(string name)
+{
+    VariableNode *currentIndex = this->head;
+    while (currentIndex != nullptr)
+    {
+        if (currentIndex->getName() == name)
+        {
+            return currentIndex;
+        }
+        currentIndex = currentIndex->getNext();
+    }
+
+    return nullptr;
+}
diff --git a/P1/VariableLinkedList.h b/P1/VariableLinkedList.h
new file mode 100644
index 0000000..14f62b0
--- /dev/null
+++ b/P1/VariableLinkedList.h
@@ -0,0 +1,22 @@
+#ifndef VARIABLELINKEDLIST_H
+#define VARIABLELINKEDLIST_H
+
+#include <iostream>
+#include <functional>
+#include "VariableNode.h"
+
+class VariableLinkedList
+{
+public:
+    bool insert(std::string name, double value);
+    VariableNode *search(std::string name);
+    bool remove(std::string name);
+    VariableLinkedList(int cap);
+    ~VariableLinkedList();
+
+private:
+    VariableNode *head;
+    int count;
+    int maxCount;
+};
+#endif
diff --git a/P1/VariableNode.cpp b/P1/VariableNode.cpp
new file mode 100644
index 0000000..f18bf19
--- /dev/null
+++ b/P1/VariableNode.cpp
@@ -0,0 +1,44 @@
+#include "VariableNode.h"
+
+using namespace std;
+
+VariableNode::VariableNode(std::string name, double value, VariableNode *next) 
+{
+    this->name = name;
+    this->value = value;
+    this->next = next;
+}
+
+string VariableNode::getName()
+{
+    return name;
+}
+
+double VariableNode::getValue()
+{
+    return value;
+}
+
+void VariableNode::setValue(double value)
+{
+    this->value = value;
+}
+
+void VariableNode::setNext(VariableNode *next)
+{
+    this->next = next; // Be careful when calling setNext, or we could have a memory leak.
+}
+
+VariableNode *VariableNode::getNext()
+{
+    return next;
+}
+
+/// @brief Delete all children nodes of this element
+void VariableNode::DestroyAll()
+{
+    if (this->next != nullptr)
+        this->next->DestroyAll();
+
+    delete this;
+}
diff --git a/P1/VariableNode.h b/P1/VariableNode.h
new file mode 100644
index 0000000..7946fd6
--- /dev/null
+++ b/P1/VariableNode.h
@@ -0,0 +1,26 @@
+#ifndef VARIABLENODE_H
+#define VARIABLENODE_H
+
+#include <iostream>
+
+class VariableNode
+{
+public:
+    std::string getName();
+
+    double getValue();
+    void setValue(double value);
+
+    VariableNode *getNext();
+    void setNext(VariableNode *next);
+
+    VariableNode(std::string name, double value, VariableNode *next);
+
+    void DestroyAll();
+
+private:
+    std::string name;
+    double value;
+    VariableNode *next;
+};
+#endif
\ No newline at end of file
diff --git a/P1/test.cpp b/P1/test.cpp
new file mode 100644
index 0000000..8b95019
--- /dev/null
+++ b/P1/test.cpp
@@ -0,0 +1,92 @@
+#include <iostream>
+#include "Calculator.h"
+
+using namespace std;
+
+int main ()
+{
+    string cmd;
+    Calculator *calc = nullptr; 
+
+    while (cin >> cmd)
+    {
+        if (cmd == "CRT")
+        {
+            int N;
+            cin >> N;
+
+            if (calc != nullptr)
+                delete calc;
+            calc = new Calculator(N);
+
+            cout << "success" << endl;
+        }
+        else if (cmd == "DEF")
+        {
+            string name;
+            double val;
+
+            cin >> name;
+            cin >> val;
+
+            if (calc->define(name, val))
+            {
+                cout << "success" << endl;
+            }
+            else
+            {
+                cout << "failure" << endl;
+            }
+        }
+        else if (cmd == "ADD" || cmd == "SUB")
+        {
+            string v1;
+            string v2;
+            string out;
+
+            cin >> v1;
+            cin >> v2;
+            cin >> out;
+
+            function<double(double, double)> operation;
+            if (cmd == "ADD")
+                operation = [](double d1, double d2) {return d1 + d2;};
+            else
+                operation = [](double d1, double d2) {return d1 - d2;};
+
+            if (calc->performOperation(v1, v2, out, operation))
+            {
+                cout << "success" << endl;
+            }
+            else
+            {
+                cout << "failure" << endl;
+            }
+        }
+        else if (cmd == "REM")
+        {
+            string name;
+
+            cin >> name;
+
+            if (calc->remove(name))
+                cout << "success" << endl;
+            else
+                cout << "failure" << endl;
+        }
+        else if (cmd == "PRT")
+        {
+            string name;
+
+            cin >> name;
+
+            calc->print(name);
+        }
+        else if (cmd == "END")
+        {
+            break;
+        }
+    }
+
+    delete calc;
+}
\ No newline at end of file
diff --git a/P2/ChainingHashTable.cpp b/P2/ChainingHashTable.cpp
new file mode 100644
index 0000000..b29da12
--- /dev/null
+++ b/P2/ChainingHashTable.cpp
@@ -0,0 +1,156 @@
+#include <iostream>
+
+#include "ChainingHashTable.h"
+#include "Process.h"
+
+ChainingHashTable::ChainingHashTable(int size)
+{
+    processList = new std::vector<Process *>[size];
+    maxCount = size;
+    count = 0;
+}
+
+ChainingHashTable::~ChainingHashTable()
+{
+    for (int i = 0; i < maxCount; i++)
+    {
+        for (int j = 0; j < processList[i].size(); j++)
+        {
+            delete processList[i][j];
+        }
+    }
+
+    delete[] processList;
+}
+
+/// @brief Insert a process into the hash table
+/// @param p the process to insert
+/// @return true if insertion was successful, false otherwise
+bool ChainingHashTable::Insert(Process *p)
+{
+    if (count >= maxCount)
+    {
+        return false;
+    }
+
+    int hashedIndex = p->getPid() % maxCount;
+
+    int indexSize = processList[hashedIndex].size();
+
+    if (indexSize == 0)
+    {
+        processList[hashedIndex].emplace_back(p);
+        count++;
+        return true;
+    }
+
+    // attempt to insert in the middle of the vector
+    for (int i = 0; i < indexSize; i++)
+    {
+        if (processList[hashedIndex][i]->getPid() == p->getPid())
+        {
+            return false;
+        }
+        // store in descending order (9, 8, 7,...)
+        if (processList[hashedIndex][i]->getPid() < p->getPid())
+        {
+            processList[hashedIndex].insert(processList[hashedIndex].begin() + i, p);
+            count++;
+            return true;
+        }
+    }
+
+    // insert at the end of the vector if we have to
+    processList[hashedIndex].emplace_back(p);
+    return true;
+}
+
+/// @brief Search the hash table for the PID
+/// @param PID the PID to search the hash table for
+/// @return the index if in the hash table, or -1 otherwise
+int ChainingHashTable::Search(unsigned int PID)
+{
+    int hashedIndex = PID % maxCount;
+
+    int indexSize = processList[hashedIndex].size();
+
+    for (int i = 0; i < indexSize; i++)
+    {
+        if (processList[hashedIndex][i]->getPid() == PID)
+        {
+            return hashedIndex;
+        }
+    }
+
+    return -1;
+}
+
+/// @brief Get a pointer to the process with PID
+/// @param PID the PID to look for
+/// @return a pointer to the process, or nullptr if the process does not exist
+Process *ChainingHashTable::Get(unsigned int PID)
+{
+    int hashedIndex = PID % maxCount;
+
+    int indexSize = processList[hashedIndex].size();
+
+    for (int i = 0; i < indexSize; i++)
+    {
+        if (processList[hashedIndex][i]->getPid() == PID)
+        {
+            return processList[hashedIndex][i];
+        }
+    }
+
+    return nullptr;
+}
+
+/// @brief Remove a process from the hash table with a given PID
+/// @param PID the PID of the process to remove
+/// @return true if the process was removed, false otherwise
+bool ChainingHashTable::Remove(unsigned int PID)
+{
+    int hashedIndex = PID % maxCount;
+
+    int indexSize = processList[hashedIndex].size();
+
+    for (int i = 0; i < indexSize; i++)
+    {
+        if (processList[hashedIndex][i]->getPid() == PID)
+        {
+            delete processList[hashedIndex][i];
+            processList[hashedIndex].erase(processList[hashedIndex].begin() + i);
+            count--;
+            return true;
+        }
+    }
+    return false;
+}
+
+/// @brief Print out the value of the chain at index m
+/// @param m the index to print the chain of
+void ChainingHashTable::Print(unsigned int m)
+{
+    if (m >= maxCount)
+    {
+        std::cout << "chain is empty" << std::endl;
+        return;
+    }
+
+    int indexSize = processList[m].size();
+
+    for (int i = 0; i < indexSize; i++)
+    {
+        if (i != 0)
+            std::cout << " ";
+
+        std::cout << processList[m][i]->getPid();
+    }
+
+    if (indexSize < 1)
+    {
+        std::cout << "chain is empty";
+    }
+
+    std::cout << std::endl;
+}
diff --git a/P2/ChainingHashTable.h b/P2/ChainingHashTable.h
new file mode 100644
index 0000000..87350ea
--- /dev/null
+++ b/P2/ChainingHashTable.h
@@ -0,0 +1,23 @@
+#ifndef CHAININGHASHTABLE_H
+#define CHAININGHASHTABLE_H
+
+#include <vector>
+#include "Process.h"
+#include "HashTable.h"
+
+class ChainingHashTable : public HashTable
+{
+public:
+    bool Insert(Process *p);
+    int Search(unsigned int PID);
+    Process *Get(unsigned int PID);
+    bool Remove(unsigned int PID);
+    void Print(unsigned int m);
+
+    ChainingHashTable(int size);
+    ~ChainingHashTable();
+
+private:
+    std::vector<Process *> *processList;
+};
+#endif
diff --git a/P2/DoubleHashTable.cpp b/P2/DoubleHashTable.cpp
new file mode 100644
index 0000000..53279dd
--- /dev/null
+++ b/P2/DoubleHashTable.cpp
@@ -0,0 +1,177 @@
+
+#include <iostream>
+#include <cmath>
+
+#include "DoubleHashTable.h"
+#include "Process.h"
+
+DoubleHashTable::DoubleHashTable(int size)
+{
+    processList = new Process *[size];
+    maxCount = size;
+    count = 0;
+
+    for (int i = 0; i < size; i++)
+    {
+        processList[i] = nullptr;
+    }
+}
+
+DoubleHashTable::~DoubleHashTable()
+{
+    for (int i = 0; i < maxCount; i++)
+    {
+        if (processList[i] != nullptr)
+            delete processList[i];
+    }
+
+    delete[] processList;
+}
+
+/// @brief Insert a process into the hash table
+/// @param p pointer to the process to insert
+/// @return true if successful, false otherwise
+bool DoubleHashTable::Insert(Process *p)
+{
+    if (count >= maxCount)
+    {
+        return false;
+    }
+
+    // Continually hash until we have reached a nullpointer, -1, or the end
+    int emptyIndex = -1;
+    for (int i = 0; i < maxCount; i++)
+    {
+        unsigned int hashedIndex = HashIndex(p->getPid(), i);
+
+        // If we have reached a nullptr, and have not seen any empty slots before
+        if (processList[hashedIndex] == nullptr && emptyIndex == -1)
+        {
+            // Replace the nullpointer with the process
+            processList[hashedIndex] = p;
+            return true;
+        }
+        // If we have reached a nullpointer and have seen an empty slot before
+        else if (processList[hashedIndex] == nullptr && emptyIndex != -1)
+        {
+            // Replace the -1 with the process
+            hashedIndex = HashIndex(p->getPid(), emptyIndex);
+            delete processList[hashedIndex];
+            processList[hashedIndex] = p;
+            return true;
+        }
+        // If we find a process with the same PID already, exit
+        else if (processList[hashedIndex]->getPid() == p->getPid())
+        {
+            return false;
+        }
+        // If we have found a slot of -1
+        else if (processList[hashedIndex]->getStartingIndex() == -1 && emptyIndex == -1)
+        {
+            // If we can insert in the empty slot (have reached the end)
+            emptyIndex = i;
+            if (!(i + 1 < maxCount))
+            {
+                delete processList[hashedIndex];
+                processList[hashedIndex] = p;
+                return true;
+            }
+        }
+    }
+
+    // Insert into the empty slot - theoretically we do not need the code in the if statement of the last else if clause, but it works...
+    if (emptyIndex != -1)
+    {
+        unsigned int hashedIndex = HashIndex(p->getPid(), emptyIndex);
+        delete processList[hashedIndex];
+        processList[hashedIndex] = p;
+        return true;
+    }
+
+    return false;
+}
+
+/// @brief Search the hash table for the given PID
+/// @param PID the pid to search for
+/// @return the index of the process, or -1 if the process does not exist
+int DoubleHashTable::Search(unsigned int PID)
+{
+    for (int i = 0; i < maxCount; i++)
+    {
+        int hashedIndex = HashIndex(PID, i);
+
+        if (hashedIndex >= maxCount || processList[hashedIndex] == nullptr)
+        {
+            return -1;
+        }
+        else if (processList[hashedIndex]->getPid() == PID)
+        {
+            return hashedIndex;
+        }
+    }
+    return -1;
+}
+
+/// @brief Search the hash table for the given PID, and return a pointer to the process object
+/// @param PID the pid to search for
+/// @return A valid process object if it exists, or a nullpointer otherwise
+Process *DoubleHashTable::Get(unsigned int PID)
+{
+    for (int i = 0; i < maxCount; i++)
+    {
+        int hashedIndex = HashIndex(PID, i);
+
+        if (hashedIndex >= maxCount || processList[hashedIndex] == nullptr)
+        {
+            return nullptr;
+        }
+        else if (processList[hashedIndex]->getPid() == PID)
+        {
+            return processList[hashedIndex];
+        }
+    }
+    return nullptr;
+}
+
+/// @brief Remove a process object from the hash table
+/// @param PID the PID of the process to remove
+/// @return true if the process was successfully removed, false otherwise
+bool DoubleHashTable::Remove(unsigned int PID)
+{
+    for (int i = 0; i < maxCount; i++)
+    {
+        int hashedIndex = HashIndex(PID, i);
+
+        if (hashedIndex >= maxCount || processList[hashedIndex] == nullptr)
+        {
+            return false;
+        }
+        else if (processList[hashedIndex]->getPid() == PID)
+        {
+            delete processList[hashedIndex];
+            processList[hashedIndex] = new Process(0, -1);
+            return true;
+        }
+    }
+    return false;
+}
+
+/// @brief Compute the hash of k and i.
+/// @param k the k value to hash (PID)
+/// @param i the i value to hash (index)
+/// @return the hashed value
+int DoubleHashTable::HashIndex(unsigned int k, int i)
+{
+    unsigned int h1 = k % maxCount;
+    unsigned int h2 = (int)std::floor(k / maxCount) % maxCount;
+
+    if (h2 % 2 == 0)
+        h2++;
+
+    return (h1 + i * h2) % maxCount;
+}
+
+void DoubleHashTable::Print(unsigned int m)
+{
+    // Not implemented
+}
diff --git a/P2/DoubleHashTable.h b/P2/DoubleHashTable.h
new file mode 100644
index 0000000..35861a0
--- /dev/null
+++ b/P2/DoubleHashTable.h
@@ -0,0 +1,24 @@
+#ifndef DOUBLEHASHTABLE_H
+#define DOUBLEHASHTABLE_H
+
+#include <vector>
+#include "Process.h"
+#include "HashTable.h"
+
+class DoubleHashTable : public HashTable
+{
+public:
+    bool Insert(Process *p);
+    int Search(unsigned int PID);
+    Process *Get(unsigned int PID);
+    bool Remove(unsigned int PID);
+    void Print(unsigned int m);
+
+    DoubleHashTable(int size);
+    ~DoubleHashTable();
+
+private:
+    Process **processList;
+    int HashIndex(unsigned int k, int i);
+};
+#endif
diff --git a/P2/HashTable.h b/P2/HashTable.h
new file mode 100644
index 0000000..099e920
--- /dev/null
+++ b/P2/HashTable.h
@@ -0,0 +1,20 @@
+#ifndef HASHTABLE_H
+#define HASHTABLE_H
+
+#include <vector>
+#include "Process.h"
+
+class HashTable
+{
+public:
+    virtual bool Insert(Process *p) = 0;
+    virtual int Search(unsigned int PID) = 0;
+    virtual Process *Get(unsigned int PID) = 0;
+    virtual bool Remove(unsigned int PID) = 0;
+    virtual void Print(unsigned int m) = 0;
+
+protected:
+    int maxCount;
+    int count;
+};
+#endif
diff --git a/P2/Makefile b/P2/Makefile
new file mode 100644
index 0000000..2628b83
--- /dev/null
+++ b/P2/Makefile
@@ -0,0 +1,2 @@
+all: test.cpp ChainingHashTable.cpp DoubleHashTable.cpp Process.cpp VirtualMemory.cpp
+	g++ -std=c++11 test.cpp ChainingHashTable.cpp DoubleHashTable.cpp Process.cpp VirtualMemory.cpp
\ No newline at end of file
diff --git a/P2/Process.cpp b/P2/Process.cpp
new file mode 100644
index 0000000..9f2f3b6
--- /dev/null
+++ b/P2/Process.cpp
@@ -0,0 +1,17 @@
+#include "Process.h"
+
+Process::Process(unsigned int PID, int startingIndex)
+{
+    this->PID = PID;
+    this->startingIndex = startingIndex;
+}
+
+unsigned int Process::getPid()
+{
+    return this->PID;
+}
+
+int Process::getStartingIndex()
+{
+    return this->startingIndex;
+}
diff --git a/P2/Process.h b/P2/Process.h
new file mode 100644
index 0000000..15e068e
--- /dev/null
+++ b/P2/Process.h
@@ -0,0 +1,16 @@
+#ifndef PROCESS_H
+#define PROCESS_H
+
+class Process
+{
+public:
+    unsigned int getPid();
+    int getStartingIndex();
+
+    Process(unsigned int PID, int startingIndex);
+
+private:
+    unsigned int PID;
+    int startingIndex;
+};
+#endif
diff --git a/P2/VirtualMemory.cpp b/P2/VirtualMemory.cpp
new file mode 100644
index 0000000..4e8f8e6
--- /dev/null
+++ b/P2/VirtualMemory.cpp
@@ -0,0 +1,136 @@
+#include <iostream>
+
+#include "VirtualMemory.h"
+#include "ChainingHashTable.h"
+#include "DoubleHashTable.h"
+
+VirtualMemory::VirtualMemory(int n, int p, bool chaining)
+{
+    if (chaining)
+    {
+        ht = new ChainingHashTable(n / p);
+    }
+    else
+    {
+        ht = new DoubleHashTable(n / p);
+    }
+
+    this->chaining = chaining;
+    this->memorySize = n;
+    this->pageSize = p;
+    this->memory = new int[n];
+
+    // push the indices onto the free memory
+    for (int i = 0; i < n / p; i++)
+    {
+        freeMemory.push_back(i);
+    }
+}
+
+VirtualMemory::~VirtualMemory()
+{
+    if (chaining)
+    {
+        delete (ChainingHashTable *)ht;
+    }
+    else
+    {
+        delete (DoubleHashTable *)ht;
+    }
+
+    delete[] memory;
+}
+
+/// @brief Allocate memory for process PID
+/// @param PID the PID to allocate memory for
+/// @return true if successful, false otherwise
+bool VirtualMemory::Insert(unsigned int PID)
+{
+    if (freeMemory.size() <= 0)
+        return false;
+
+    int memoryIndex = freeMemory.back();
+    freeMemory.pop_back();
+
+    Process *p = new Process(PID, memoryIndex);
+    if (!ht->Insert(p))
+    {
+        delete p;
+        freeMemory.push_back(memoryIndex);
+        return false;
+    }
+
+    return true;
+}
+
+/// @brief Search the hash table for the index of PID
+/// @param PID the PID of the process to search for
+/// @return the index of the process object, -1 if the object does not exist
+int VirtualMemory::Search(unsigned int PID)
+{
+    return ht->Search(PID);
+}
+
+/// @brief Write to a process's memory
+/// @param PID The PID of the memory to write to
+/// @param addr The virtual address of the memory to write to
+/// @param x The value to write into memory
+/// @return true if successful, false otherwise
+bool VirtualMemory::Write(unsigned int PID, int addr, int x)
+{
+    if (addr >= pageSize || addr < 0)
+        return false;
+
+    Process *p = ht->Get(PID);
+
+    // if we do not have any memory allocated to PID
+    if (p == nullptr)
+        return false;
+
+    memory[p->getStartingIndex() * pageSize + addr] = x;
+    return true;
+}
+
+/// @brief Read the memory
+/// @param PID The PID of the process to read memory of
+/// @param addr The virtual address of memory to read from
+void VirtualMemory::Read(unsigned int PID, int addr)
+{
+    if (addr >= pageSize)
+    {
+        std::cout << "failure" << std::endl;
+        return;
+    }
+
+    Process *p = ht->Get(PID);
+    // if we do not have any memory allocated to PID
+    if (p == nullptr)
+    {
+        std::cout << "failure" << std::endl;
+        return;
+    }
+
+    std::cout << addr << " " << memory[p->getStartingIndex() * pageSize + addr] << std::endl;
+}
+
+/// @brief Deallocate memory from process PID.
+/// @param PID The PID of the process to dealocate memory from
+/// @return true if successful, false otherwise
+bool VirtualMemory::Delete(unsigned int PID)
+{
+    Process *p = ht->Get(PID);
+
+    if (p == nullptr)
+        return false;
+
+    freeMemory.push_back(p->getStartingIndex());
+
+    return ht->Remove(PID);
+}
+
+/// @brief Print the chain of the hash table at index m
+/// @param m the index of the chain to print
+void VirtualMemory::Print(int m)
+{
+    ht->Print(m);
+}
diff --git a/P2/VirtualMemory.h b/P2/VirtualMemory.h
new file mode 100644
index 0000000..ec20f68
--- /dev/null
+++ b/P2/VirtualMemory.h
@@ -0,0 +1,30 @@
+#ifndef VIRTUALMEMORY_H
+#define VIRTUALMEMORY_H
+
+#include "Process.h"
+#include "HashTable.h"
+
+class VirtualMemory
+{
+public:
+    VirtualMemory(int n, int p, bool chaining);
+    ~VirtualMemory();
+
+    bool Insert(unsigned int PID);
+    int Search(unsigned int PID);
+
+    bool Write(unsigned int PID, int addr, int x);
+    void Read(unsigned int PID, int addr);
+
+    bool Delete(unsigned int PID);
+    void Print(int m);
+
+private:
+    HashTable *ht;
+    int memorySize;
+    int pageSize;
+    int *memory;
+    std::vector<int> freeMemory;
+    bool chaining;
+};
+#endif
diff --git a/P2/test.cpp b/P2/test.cpp
new file mode 100644
index 0000000..5493d49
--- /dev/null
+++ b/P2/test.cpp
@@ -0,0 +1,103 @@
+#include <iostream>
+
+#include "VirtualMemory.h"
+
+using namespace std;
+
+int main()
+{
+    string cmd;
+    VirtualMemory *vm = nullptr;
+    bool chaining = true;
+
+    while (cin >> cmd)
+    {
+        if (cmd == "OPEN")
+        {
+            chaining = false;
+        }
+        else if (cmd == "ORDERED")
+        {
+            chaining = true;
+        }
+        if (cmd == "M")
+        {
+            int N;
+            int P;
+            cin >> N;
+            cin >> P;
+
+            vm = new VirtualMemory(N, P, chaining);
+
+            cout << "success" << endl;
+        }
+        else if (cmd == "INSERT")
+        {
+            unsigned int PID;
+            cin >> PID;
+
+            if (vm->Insert(PID))
+                cout << "success" << endl;
+            else
+                cout << "failure" << endl;
+        }
+        else if (cmd == "SEARCH")
+        {
+            unsigned int PID;
+            cin >> PID;
+
+            int ret = vm->Search(PID);
+            if (ret == -1)
+                cout << "not found" << endl;
+            else
+                cout << "found " << PID << " in " << ret << endl;
+        }
+        else if (cmd == "WRITE")
+        {
+            unsigned int PID;
+            int ADDR;
+            int x;
+
+            cin >> PID;
+            cin >> ADDR;
+            cin >> x;
+
+            if (vm->Write(PID, ADDR, x))
+                cout << "success" << endl;
+            else
+                cout << "failure" << endl;
+        }
+        else if (cmd == "READ")
+        {
+            unsigned int PID;
+            int ADDR;
+
+            cin >> PID;
+            cin >> ADDR;
+
+            vm->Read(PID, ADDR);
+        }
+        else if (cmd == "DELETE")
+        {
+            unsigned int PID;
+            cin >> PID;
+
+            if (vm->Delete(PID))
+                cout << "success" << endl;
+            else
+                cout << "failure" << endl;
+        }
+        else if (cmd == "PRINT")
+        {
+            int m;
+            cin >> m;
+
+            vm->Print(m);
+        }
+        else if (cmd == "END")
+        {
+            break;
+        }
+    }
+    delete vm;
+}
diff --git a/P3/Makefile b/P3/Makefile
new file mode 100644
index 0000000..04bdd81
--- /dev/null
+++ b/P3/Makefile
@@ -0,0 +1,2 @@
+all: trietest.cpp Trie.cpp
+	g++ -std=c++11 trietest.cpp Trie.cpp
\ No newline at end of file
diff --git a/P3/Trie.cpp b/P3/Trie.cpp
new file mode 100644
index 0000000..aaba389
--- /dev/null
+++ b/P3/Trie.cpp
@@ -0,0 +1,218 @@
+#include "Trie.h"
+#include "illegal_exception.h"
+
+Trie::Trie()
+{
+    children = new Trie *[MAX_SLOTS];
+    isEnd = false;
+    for (int i = 0; i < MAX_SLOTS; i++)
+    {
+        children[i] = nullptr;
+    }
+    count = 0;
+}
+
+Trie::~Trie()
+{
+    delete[] children;
+}
+
+/// @brief Wrapper function to recursively insert string s into the trie.
+/// @param s The string to insert into the trie.
+/// @return True if the string was inserted, false otherwise.
+bool Trie::Insert(std::string s)
+{
+    // Wrapper function is needed to meet illegal_exception criteria without having O(n^2) runtime (recursive function).
+    for (int i = 0; i < s.length(); i++)
+    {
+        if (s[i] < ASCII_FACTOR || s[i] > ASCII_UPPER)
+        {
+            throw illegal_exception();
+        }
+    }
+    return PerformInsert(s);
+}
+
+/// @brief Recursive function to insert string s into the trie.
+/// @param s The string to insert into the trie.
+/// @return True if the string was inserted successfully, false otherwise.
+bool Trie::PerformInsert(std::string s)
+{
+    if (s.length() > 0) // Add until there are no more characters.
+    {
+        char c = s.at(0);
+        // Create the new trie if it does not exist. This condition will never be true if the word cannot be inserted.
+        if (children[c - ASCII_FACTOR] == nullptr)
+            children[c - ASCII_FACTOR] = new Trie(); 
+
+        // Recursively insert, checking if the previous insertion was successful (if so, increment count).
+        if (children[c - ASCII_FACTOR]->PerformInsert(s.substr(1)))
+        {
+            count++;
+            return true;
+        }
+    }
+    // If there are no characters and we have not reached a word end then the word is not already added.
+    else if (!this->isEnd) 
+    {
+        this->isEnd = true;
+        count++;
+        return true;
+    }
+    return false; // If the word is already in the trie, return false.
+}
+
+/// @brief Wrapper function to remove an element from the trie. 
+/// @param s The string to remove from the trie.
+/// @return True if the element was removed successfully, false otherwise.
+bool Trie::Remove(std::string s)
+{
+    // Achieve O(n) runtime using wrapper function.
+    for (int i = 0; i < s.length(); i++)
+    {
+        if (s[i] < ASCII_FACTOR || s[i] > ASCII_UPPER)
+        {
+            throw illegal_exception();
+        }
+    }
+    return PerformRemove(s);
+}
+
+/// @brief Recursively remove string s from the trie.
+/// @param s The string to remove from the trie.
+/// @return True if the string was removed, false otherwise.
+bool Trie::PerformRemove(std::string s)
+{
+    if (s.length() > 0) // Remove until there are no more characters to remove.
+    {
+        // If we have reached a trie that does not have the correct child, we cannot remove the word.
+        char c = s.at(0);
+        if (children[c - ASCII_FACTOR] == nullptr)
+            return false;
+
+        // Recursively remove the remaining bit of the word. Subtracting from the count if successful.
+        if (children[c - ASCII_FACTOR]->PerformRemove(s.substr(1)))
+        {
+            count--;
+
+            // Free any child tries that have a count of 0. These are guaranteed to have no children.
+            for (int i = 0; i < MAX_SLOTS; i++) 
+            {
+                if (children[i] != nullptr && children[i]->IsEmpty())
+                {
+                    delete children[i];
+                    children[i] = nullptr;
+                }
+            }
+
+            return true; // If previous removes were successful, this remove is also successful.
+        }
+    }
+    // If we have reached the end of the word, we can succesfully remove it from the trie.
+    else if (this->isEnd)
+    {
+        this->isEnd = false;
+        count--;
+        return true;
+    }
+
+    return false; // When we are out of characters, but did not find a word end, cannot remove.
+}
+
+/// @brief Determine if the trie is empty.
+/// @return True if the trie is empty, false otherwise.
+bool Trie::IsEmpty()
+{
+    return count == 0;
+}
+
+/// @brief Empty the trie.
+void Trie::Clear()
+{
+    // We do not need to worry about dangling pointers, since everything is being deleted in order.
+    for (int i = 0; i < MAX_SLOTS; i++)
+    {
+        if (children[i] != nullptr)
+            children[i]->Clear(); // Recursively delete any non-null pointer children.
+    }
+
+    delete this;
+}
+
+/// @brief Perform a depth first search on the trie for string s, outputting the result by performing in place modification of the vector out.
+/// @param out 
+/// @param s 
+void Trie::DepthFirstSearch(std::vector<std::string> *out, std::string s)
+{
+    if (isEnd)
+        out->push_back(s); // If we have reached the end, put the word into the output
+
+    // Recursively search children nodes, in order from A-Z.
+    for (int i = 0; i < MAX_SLOTS; i++)
+    {
+        if (children[i] != nullptr)
+            children[i]->DepthFirstSearch(out, s + (char)(i + ASCII_FACTOR));
+    }
+}
+
+/// @brief Get the number of words in the trie.
+/// @return An integer of the number of words in the trie.
+int Trie::Size()
+{
+    return count;
+}
+
+/// @brief Wrapper function to count the number of suffixes for a given string s.
+/// @param s 
+/// @return 
+int Trie::CountSuffixes(std::string s)
+{
+    for (int i = 0; i < s.length(); i++)
+    {
+        if (s[i] < ASCII_FACTOR || s[i] > ASCII_UPPER)
+        {
+            throw illegal_exception();
+        }
+    }
+    return PerformCountSuffixes(s);
+}
+
+
+int Trie::PerformCountSuffixes(std::string s)
+{
+    if (s.empty())
+        return count;
+
+    char c = s.at(0);
+    int index = c - ASCII_FACTOR;
+
+    if (children[index] != nullptr)
+        return children[index]->PerformCountSuffixes(s.substr(1));
+    else
+        return 0; 
+}
+
+bool Trie::SpellCheck(std::vector<std::string> *out, std::string check, std::string s)
+{
+    if (check.empty() && isEnd)
+        return true;
+    else if (check.empty())
+        return false;
+
+    char c = check.at(0);
+    int index = c - ASCII_FACTOR;
+;
+    if (children[index] != nullptr)
+    {
+        if (children[index]->SpellCheck(out, check.substr(1), s + c))
+        {
+            return true;
+        }
+        else
+        {
+            children[index]->DepthFirstSearch(out, s + c);
+            return true;
+        }
+    }
+    return false;
+}
diff --git a/P3/Trie.h b/P3/Trie.h
new file mode 100644
index 0000000..6cd5ec6
--- /dev/null
+++ b/P3/Trie.h
@@ -0,0 +1,33 @@
+#ifndef TRIE_H
+#define TRIE_H
+
+#include <iostream>
+#include <vector>
+
+class Trie
+{
+public:
+    Trie();
+    ~Trie();
+    bool Insert(std::string s);
+    bool Remove(std::string s);
+    void DepthFirstSearch(std::vector<std::string> *out, std::string s);
+    bool IsEmpty();
+    void Clear();
+    int Size();
+    int CountSuffixes(std::string s);
+    bool SpellCheck(std::vector<std::string> *out, std::string check, std::string s);
+
+private:
+    const int MAX_SLOTS = 26;
+    const int ASCII_FACTOR = 65;
+    const int ASCII_UPPER = 90;
+    int count;
+    bool isEnd;
+    Trie **children;
+
+    bool PerformInsert(std::string s);
+    bool PerformRemove(std::string s);
+    int PerformCountSuffixes(std::string s);
+};
+#endif
\ No newline at end of file
diff --git a/P3/illegal_exception.h b/P3/illegal_exception.h
new file mode 100644
index 0000000..bf45886
--- /dev/null
+++ b/P3/illegal_exception.h
@@ -0,0 +1,8 @@
+#ifndef ILLEGAL_EXCEPTION_H
+#define ILLEGAL_EXCEPTION_H
+
+#include <exception>
+
+class illegal_exception : std::exception {};
+
+#endif
diff --git a/P3/trietest.cpp b/P3/trietest.cpp
new file mode 100644
index 0000000..b502584
--- /dev/null
+++ b/P3/trietest.cpp
@@ -0,0 +1,153 @@
+#include <iostream>
+#include <fstream>
+#include "Trie.h"
+#include <vector>
+#include "illegal_exception.h"
+
+using namespace std;
+
+const string FILE_NAME = "corpus.txt";
+
+void PrintVector(vector<string> *out)
+{
+    for (int i = 0; i < out->size(); i++)
+    {
+        cout << (*out)[i];
+        if (i < out->size() - 1)
+            cout << " ";
+    }
+}
+
+int main()
+{
+    string cmd;
+    string addWord;
+    ifstream fin(FILE_NAME);
+    Trie *trie = new Trie();
+
+    while (cin >> cmd)
+    {
+        if (cmd == "load")
+        {
+            if (!fin.is_open())
+                fin.open(FILE_NAME);
+
+            while (fin >> addWord)
+            {
+                trie->Insert(addWord);
+            }
+
+            fin.close();
+            cout << "success" << endl;
+        }
+        else if (cmd == "i")
+        {
+            string word;
+            cin >> word;
+            try
+            {
+                if (trie->Insert(word))
+                    cout << "success" << endl;
+                else
+                    cout << "failure" << endl;
+            }
+            catch (illegal_exception e)
+            {
+                cout << "illegal argument" << endl;
+            }
+        }
+        else if (cmd == "e")
+        {
+            string word;
+            cin >> word;
+
+            try
+            {
+                if (trie->Remove(word))
+                    cout << "success" << endl;
+                else
+                    cout << "failure" << endl;
+            }
+            catch (illegal_exception e)
+            {
+                cout << "illegal argument" << endl;
+            }
+        }
+        else if (cmd == "clear")
+        {
+            trie->Clear();
+            trie = new Trie();
+            cout << "success" << endl;
+        }
+        else if (cmd == "size")
+        {
+            cout << "number of words is " << trie->Size() << endl;
+        }
+        else if (cmd == "empty")
+        {
+            if (trie->IsEmpty())
+                cout << "empty 1" << endl;
+            else
+                cout << "empty 0" << endl;
+        }
+        else if (cmd == "spellcheck")
+        {
+            string word;
+            cin >> word;
+
+            vector<string> out;
+
+            bool result = trie->SpellCheck(&out, word, "");
+
+            if (out.empty() && result)
+            {
+                cout << "correct" << endl;
+            }
+            else if (!result)
+            {
+                cout << endl;
+            }
+            else
+            {
+                PrintVector(&out);
+                cout << endl;
+            }
+        }
+        else if (cmd == "p")
+        {
+            vector<string> out;
+            trie->DepthFirstSearch(&out, "");
+
+            PrintVector(&out);
+
+            if (out.size() > 0)
+                cout << endl;
+            
+        }
+
+        else if (cmd == "c")
+        {
+            string prefix;
+            cin >> prefix;
+
+            try
+            {
+                int count = trie->CountSuffixes(prefix);
+
+                if (count != -1 && count != 0)
+                    cout << "count is " << count << endl;
+                else
+                    cout << "not found" << endl;
+            }
+            catch (illegal_exception e)
+            {
+                cout << "illegal argument" << endl;
+            }
+        }
+        else if (cmd == "exit")
+        {
+            break;
+        }
+    }
+    trie->Clear();
+}
diff --git a/P4/Graph.cpp b/P4/Graph.cpp
new file mode 100644
index 0000000..42f1366
--- /dev/null
+++ b/P4/Graph.cpp
@@ -0,0 +1,189 @@
+#include "Graph.h"
+#include <limits.h>
+#include "PriorityQueue.h"
+#include "illegal_exception.h"
+
+/// @brief Create a new graph
+/// @param maxCount The maximum number of elements the graph is required to store
+/// @param mst A flag to enable MST (enabling makes the runtime of the graph worse)
+Graph::Graph(int maxCount, bool mst)
+{
+    vertexList.reserve(maxCount);
+    if (!mst)
+        pq = new PriorityQueue(maxCount);
+    this->maxCount = maxCount;
+    this->mstEnabled = mst;
+}
+
+Graph::~Graph()
+{
+    delete pq;
+}
+
+/// @brief Insert an edge from vertex a to b, with weight w. When MST flag is true, it is invalid to pass in edges that already exist in the graph.
+/// @param a Vertex a
+/// @param b Vertex b
+/// @param weight The weight of the edge to insert
+/// @return True if successful, false otherwise
+/// @throws illegal_exception if given invalid input
+bool Graph::Insert(int a, int b, int weight)
+{
+    // Check input validity
+    if (a > 50000 || a < 1 || b > 50000 || b < 1 || weight < 1)
+    {
+        throw illegal_exception();
+    }
+
+    // Check if the node already exists. Skip this check when the MST is disabled - allows efficient inserts for building tree.
+    int count = adjacencyList[a].size();
+    if (!mstEnabled)
+    {
+
+        for (int i = 0; i < count; i++)
+        {
+            int currentData = std::get<0>(adjacencyList[a][i]);
+            if (currentData == b)
+                return false;
+        }
+    }
+
+    // Add the b vertex to the adjacency list for a
+    adjacencyList[a].push_back(std::make_tuple(b, weight));
+
+    // Add the vertex a to the vertexList, if a has never been added to the graph
+    if (count == 0)
+        vertexList.insert(vertexList.begin() + vertexList.size(), std::make_tuple(a, INT_MAX, -1));
+
+    // Add a vertex to the adjacency list for b, and insert b into vertexList if required
+    count = adjacencyList[b].size();
+    adjacencyList[b].push_back(std::make_tuple(a, weight));
+    if (count == 0)
+        vertexList.insert(vertexList.begin() + vertexList.size(), std::make_tuple(b, INT_MAX, -1));
+
+    return true;
+}
+
+/// @brief Delete vertex a from the graph.
+/// @param a The vertex to delete from the graph.
+/// @return True if successful, false otherwise.
+/// @throws illegal_exception if given invalid input.
+bool Graph::Delete(int a)
+{
+    // Check input conditions
+    if (a > 50000 || a < 1)
+    {
+        throw illegal_exception();
+    }
+
+    // Ensure the vertex is in the graph
+    int count = adjacencyList[a].size();
+    if (count == 0)
+        return false;
+
+    // Remove all references to the vertex in the adjacency lists of other vertices, and in the vertexList.
+    while (count != 0)
+    {
+        std::tuple<int, int> lastData = adjacencyList[a][count - 1];
+        adjacencyList[a].pop_back();
+
+        // Remove vertex from all adjacency lists
+        for (int j = 0; j < adjacencyList[std::get<0>(lastData)].size(); j++)
+        {
+            if (std::get<0>(adjacencyList[std::get<0>(lastData)][j]) == a)
+            {
+                adjacencyList[std::get<0>(lastData)].erase(adjacencyList[std::get<0>(lastData)].begin() + j);
+            }
+        }
+
+        // If removing vertex a causes any adjacency lists to become empty, remove that vertex from the vertexList.
+        if (adjacencyList[std::get<0>(lastData)].size() < 1)
+        {
+            for (int j = 0; j < vertexList.size(); j++)
+            {
+                if (std::get<0>(vertexList[j]) == std::get<0>(lastData))
+                    vertexList.erase(vertexList.begin() + j);
+            }
+        }
+
+        count--;
+    }
+
+    // Remove a from the vertex list.
+    for (int i = 0; i < vertexList.size(); i++)
+    {
+        if (std::get<0>(vertexList[i]) == a)
+            vertexList.erase(vertexList.begin() + i);
+    }
+
+    return true;
+}
+
+/// @brief Get a vector containing the adjacent vertices to a
+/// @param a The vertex to check
+/// @return A vector of all vertices
+/// @throws illegal_exception if given invalid input.
+std::vector<std::tuple<int, int>> *Graph::GetAdjacent(int a)
+{
+    if (a > 50000 || a < 1)
+    {
+        throw illegal_exception();
+    }
+
+    return &adjacencyList[a];
+}
+
+/// @brief Compute the MST of the graph
+/// @param out A vector to output the resulting MST edges in
+/// @return The cost of the MST
+int Graph::MST(std::vector<std::tuple<int, int, int>> *out)
+{
+    // If there are no nodes, or somehow only one node.
+    if (vertexList.size() < 2)
+        return 0;
+
+    // When there is only one edge, that edge is the MST
+    if (vertexList.size() < 3)
+    {
+        out->push_back(std::make_tuple(std::get<0>(vertexList[0]), std::get<0>(vertexList[1]), std::get<1>(adjacencyList[std::get<0>(vertexList[0])][0])));
+        return std::get<1>(adjacencyList[std::get<0>(vertexList[0])][0]);
+    }
+
+    // Attribution: Some of the Pseudocode used to write this function is from the CLRS textbook.
+    int cost = 0;
+    pq->Init(&vertexList);
+
+    // Apply Prim's Algorithm using a PriorityQueue.
+    // Extract elements from the PQ until it is empty
+    while (!pq->IsEmpty())
+    {
+        // Extract the element with the lowest weight
+        std::tuple<int, int, int> u = pq->HeapExtractMin();
+
+        // Prevent insertion of first node (or any infinite weights).
+        if (std::get<1>(u) != INT_MAX)
+        {
+            out->push_back(std::make_tuple(std::get<2>(u), std::get<0>(u), std::get<1>(u)));
+            cost += std::get<1>(u);
+        }
+
+        // Iterate through all of the adjacent vertices
+        for (int i = 0; i < adjacencyList[std::get<0>(u)].size(); i++)
+        {
+            std::tuple<int, int> v = adjacencyList[std::get<0>(u)][i]; // The vertex being examined
+
+            // If the current path is better than the stored path, update it.
+            if (pq->Contains(std::get<0>(v)) && std::get<1>(v) < pq->GetKey(std::get<0>(v)))
+            {
+                pq->Modify(std::get<0>(v), std::get<1>(v), std::get<0>(u));
+            }
+        }
+    }
+    return cost;
+}
+
+/// @brief Get the number of vertices in the graph
+/// @return The number of vertices in the graph
+int Graph::GetVertexCount()
+{
+    return vertexList.size();
+}
diff --git a/P4/Graph.h b/P4/Graph.h
new file mode 100644
index 0000000..fef3866
--- /dev/null
+++ b/P4/Graph.h
@@ -0,0 +1,27 @@
+#ifndef TRIE_H
+#define TRIE_H
+
+#include <iostream>
+#include <vector>
+#include <tuple>
+#include "PriorityQueue.h"
+
+class Graph
+{
+public:
+    Graph(int maxCount, bool mst);
+    ~Graph();
+    bool Insert(int a, int b, int weight);
+    bool Delete(int a);
+    std::vector<std::tuple<int, int>> *GetAdjacent(int a);
+    int GetVertexCount();
+    int MST(std::vector<std::tuple<int, int, int>> *outList);
+
+private:
+    PriorityQueue *pq;
+    std::vector<std::tuple<int, int>> adjacencyList[50001]; // An array of vectors of tuples <node2, weight>
+    std::vector<std::tuple<int, int, int>> vertexList;      // List of all vertices in the graph stored as <node1, inf, -1>
+    int maxCount;
+    bool mstEnabled;
+};
+#endif
diff --git a/P4/Makefile b/P4/Makefile
new file mode 100644
index 0000000..76ab158
--- /dev/null
+++ b/P4/Makefile
@@ -0,0 +1,2 @@
+all: Test.cpp Graph.cpp PriorityQueue.cpp
+	g++ -std=c++11 Test.cpp Graph.cpp PriorityQueue.cpp
diff --git a/P4/PriorityQueue.cpp b/P4/PriorityQueue.cpp
new file mode 100644
index 0000000..aaa7dab
--- /dev/null
+++ b/P4/PriorityQueue.cpp
@@ -0,0 +1,153 @@
+#include "PriorityQueue.h"
+#include <limits>
+
+// Attribution: Some of the Pseudocode used to write these functions is from the CLRS textbook.
+
+PriorityQueue::PriorityQueue(int maxCount)
+{
+    count = 0;
+    locations.reserve(maxCount);
+    arr.reserve(maxCount);
+    for (int i = 0; i < maxCount; i++)
+    {
+        locations[i] = -1;
+    }
+}
+
+/// @brief Initialize the priority queue with the given vector of tuples. The tuples should be in the format: <vertex, weight, parent>
+/// @param vertexList The vector of tuples to insert into the priority queue.
+void PriorityQueue::Init(std::vector<std::tuple<int, int, int>> *vertexList)
+{
+    count = vertexList->size();
+
+    for (int i = 0; i < count; i++)
+    {
+        arr[i] = vertexList->at(i);
+        locations[std::get<0>(vertexList->at(i))] = i;
+    }
+}
+
+/// @brief Modify the weight and/or the parent of vertex v
+/// @param v The vertex to modify (not the index in the priority queue)
+/// @param w The weight to set
+/// @param parent The parent to set
+/// @return True if successful, false otherwise
+bool PriorityQueue::Modify(int v, int w, int parent)
+{
+    if (count < 1)
+        return false;
+
+    int i = locations[v];
+    if (i < 0)
+        return false;
+
+    std::get<1>(arr[i]) = w;
+    std::get<2>(arr[i]) = parent;
+    while (i > 0 && std::get<1>(arr[Parent(i)]) > std::get<1>(arr[i]))
+    {
+
+        Exchange(i, Parent(i));
+        i = Parent(i);
+    }
+    return true;
+}
+
+/// @brief Extract the smallest value from the priority queue (the topmost element, since this is a min pq).
+/// @return The element in the priority queue if not empty, or a tuple of all ints <-1, -1, -1> if empty
+std::tuple<int, int, int> PriorityQueue::HeapExtractMin()
+{
+    // Signal no minimum element if there are no elements.
+    if (IsEmpty())
+        return std::make_tuple<int, int, int>(-1, -1, -1);
+
+    std::tuple<int, int, int> min = arr[0];
+
+    locations[std::get<0>(arr[count - 1])] = 0;
+    locations[std::get<0>(min)] = -1;
+    arr[0] = arr[count - 1];
+    count--;
+    MinHeapify(0);
+    return min;
+}
+
+/// @brief Run the MinHeapify algorithm on the pq.
+/// @param i The index (not the vertex).
+void PriorityQueue::MinHeapify(int i)
+{
+    int l = Left(i);
+    int r = Right(i);
+
+    int smallest = i;
+
+    if (l < count && std::get<1>(arr[l]) < std::get<1>(arr[i]))
+        smallest = l;
+
+    if (r < count && std::get<1>(arr[r]) < std::get<1>(arr[smallest]))
+        smallest = r;
+
+    if (smallest != i)
+    {
+        Exchange(i, smallest);
+        MinHeapify(smallest);
+    }
+}
+
+/// @brief Get a boolean value to determine if the priority queue is empty
+/// @return True if the priority queue is empty, false otherwise.
+bool PriorityQueue::IsEmpty()
+{
+    return count < 1;
+}
+
+/// @brief Check if the priority queue contains a vertex v.
+/// @param v The vertex (not index) to check.
+/// @return True if the vertex (not index) is contained in the priority queue, false otherwise.
+bool PriorityQueue::Contains(int v)
+{
+    return locations[v] != -1;
+}
+
+/// @brief Get the key (weight) of a vertex (not index) in the priority queue
+/// @param v The vertex (not index) to get the weight for
+/// @return The key (weight) of the vertex
+int PriorityQueue::GetKey(int v)
+{
+    return std::get<1>(arr[locations[v]]);
+}
+
+/// @brief Swap the elements of index a and index b (not the vertex number)
+/// @param a The index (not vertex) of the element to swap
+/// @param b The index (not vertex) of the element to swap
+void PriorityQueue::Exchange(int a, int b)
+{
+    locations[std::get<0>(arr[a])] = b;
+    locations[std::get<0>(arr[b])] = a;
+
+    std::tuple<int, int, int> temp = arr[a];
+    arr[a] = arr[b];
+    arr[b] = temp;
+}
+
+/// @brief Given an index (not vertex), get the parent of that index (not vertex)
+/// @param i The index (not vertex) to get the parent of
+/// @return The index (not vertex) of the parent
+int PriorityQueue::Parent(int i)
+{
+    return (i - 1) / 2;
+}
+
+/// @brief Given an index (not vertex), get the left child of that index (not vertex)
+/// @param i The index (not vertex) to get the left child of
+/// @return The index (not vertex) of the left child
+int PriorityQueue::Left(int i)
+{
+    return 2 * i + 1;
+}
+
+/// @brief Given an index (not vertex), get the right child of that index (not vertex)
+/// @param i The index (not vertex) to get the right child of
+/// @return The index (not vertex) of the right child
+int PriorityQueue::Right(int i)
+{
+    return 2 * i + 2;
+}
diff --git a/P4/PriorityQueue.h b/P4/PriorityQueue.h
new file mode 100644
index 0000000..ce4d17d
--- /dev/null
+++ b/P4/PriorityQueue.h
@@ -0,0 +1,31 @@
+#ifndef PRIORITYQUEUE_H
+#define PRIORITYQUEUE_H
+
+#include <iostream>
+#include <vector>
+#include <tuple>
+
+class PriorityQueue
+{
+public:
+    PriorityQueue(int maxCount);
+    void Init(std::vector<std::tuple<int, int, int>> *vertexList);
+    std::tuple<int, int, int> HeapExtractMin();
+    bool Modify(int i, int w, int parent);
+    bool Contains(int v);
+    bool IsEmpty();
+    int GetKey(int v);
+
+private:
+    int count;
+    void Exchange(int a, int b);
+    void MinHeapify(int i);
+    int Parent(int i);
+    int Left(int i);
+    int Right(int i);
+    std::vector<std::tuple<int, int, int>> arr; // The actual priority queue.
+    std::vector<int> locations;                 // References for vertex -> PQ index. Allows indexing PQ in O(1) time.
+    const int MAX_UNIQUE_KEYS = 50001;
+};
+
+#endif
diff --git a/P4/Test.cpp b/P4/Test.cpp
new file mode 100644
index 0000000..e8be2d5
--- /dev/null
+++ b/P4/Test.cpp
@@ -0,0 +1,180 @@
+#include <iostream>
+#include <fstream>
+#include "Graph.h"
+#include "illegal_exception.h"
+
+using namespace std;
+
+const int MAX_NODE_COUNT = 50001;
+
+int main()
+{
+    string cmd;
+    Graph *graph = new Graph(MAX_NODE_COUNT, false);
+    bool mstModified = true;
+    int prevCost = 0;
+    std::vector<std::tuple<int, int, int>> prevOutput;
+
+    while (cin >> cmd)
+    {
+        if (cmd == "LOAD")
+        {
+            mstModified = true;
+            string filename;
+            cin >> filename;
+
+            ifstream fin(filename.c_str());
+
+            int count;
+            fin >> count;
+
+            int n1;
+            while (fin >> n1)
+            {
+                int n2;
+                fin >> n2;
+                int w;
+                fin >> w;
+
+                graph->Insert(n1, n2, w);
+            }
+
+            fin.close();
+            cout << "success" << endl;
+        }
+        else if (cmd == "INSERT")
+        {
+            int a;
+            int b;
+            int w;
+
+            cin >> a;
+            cin >> b;
+            cin >> w;
+
+            try
+            {
+                if (graph->Insert(a, b, w))
+                {
+                    mstModified = true;
+                    std::cout << "success" << std::endl;
+                }
+                    
+                else
+                {
+                    std::cout << "failure" << std::endl;
+                }
+            }
+            catch (illegal_exception)
+            {
+                std::cout << "illegal argument" << std::endl;
+            }
+        }
+        else if (cmd == "DELETE")
+        {
+            int a;
+            cin >> a;
+
+            try
+            {
+                if (graph->Delete(a))
+                {
+                    mstModified = true;
+                    std::cout << "success" << std::endl;
+                }
+                else
+                {
+                    std::cout << "failure" << std::endl;
+                }
+            }
+            catch (illegal_exception)
+            {
+                std::cout << "illegal argument" << std::endl;
+            }
+        }
+        else if (cmd == "PRINT")
+        {
+            int a;
+            cin >> a;
+
+            try
+            {
+                std::vector<std::tuple<int, int>> *out = graph->GetAdjacent(a);
+                for (int i = 0; i < out->size(); i++)
+                {
+                    std::cout << get<0>(out->at(i)) << " ";
+                }
+
+                if (out->size() < 1)
+                {
+                    std::cout << "failure";
+                }
+                std::cout << endl;
+            }
+            catch (illegal_exception)
+            {
+                std::cout << "illegal argument" << std::endl;
+            }
+        }
+        else if (cmd == "MST")
+        {
+            // Prevent useless regeneration of MST.
+            if (!mstModified)
+            {
+                if (prevOutput.size() < 1)
+                    std::cout << "failure";
+
+                for (int i = 0; i < prevOutput.size(); i++)
+                {
+                    std::cout << std::get<0>(prevOutput[i]) << " " << std::get<1>(prevOutput[i]) << " " << std::get<2>(prevOutput[i]) << " ";
+                }
+
+                std::cout << std::endl;
+            }
+            else
+            {
+                std::vector<std::tuple<int, int, int>> out;
+                out.reserve(graph->GetVertexCount());
+                prevCost = graph->MST(&out);
+                prevOutput = out;
+
+                for (int i = 0; i < out.size(); i++)
+                {
+                    std::cout << std::get<0>(out[i]) << " " << std::get<1>(out[i]) << " " << std::get<2>(out[i]) << " ";
+                }
+
+                if (out.size() < 1)
+                    std::cout << "failure";
+
+                std::cout << std::endl;
+                mstModified = false;
+            }
+        }
+        else if (cmd == "COST")
+        {
+            // Prevent useless regeneration of MST.
+            if (!mstModified)
+            {
+                std::cout << "cost is " << prevCost << std::endl;
+            }
+            else
+            {
+                std::vector<std::tuple<int, int, int>> out;
+                out.reserve(graph->GetVertexCount());
+                int cost = graph->MST(&out);
+                prevOutput = out;
+                prevCost = cost;
+
+                std::cout << "cost is " << cost << std::endl;
+                mstModified = false;
+            }
+        }
+
+        else if (cmd == "END")
+        {
+            break;
+        }
+    }
+
+    delete graph;
+}
diff --git a/P4/illegal_exception.h b/P4/illegal_exception.h
new file mode 100644
index 0000000..fe379b6
--- /dev/null
+++ b/P4/illegal_exception.h
@@ -0,0 +1,10 @@
+#ifndef ILLEGAL_EXCEPTION_H
+#define ILLEGAL_EXCEPTION_H
+
+#include <exception>
+
+class illegal_exception : std::exception
+{
+};
+
+#endif