Day 11

2023/day11/p1.rb

@@ -0,0 +1,46 @@
+# frozen_string_literal: true
+
+def build_space_arr(grid)
+  offset = []
+  grid.each_with_index do |row, i|
+    offset << if row.include? '#'
+                if offset.empty?
+                  0
+                else
+                  offset[i - 1] + 1
+                end
+              elsif offset.empty?
+                1
+              else
+                offset[i - 1] + 2
+              end
+  end
+  offset
+end
+
+res = 0
+grid = []
+File.foreach('./2023/day11/data') do |line|
+  grid << line.strip.split('')
+end
+
+row_offset = build_space_arr grid
+col_offset = build_space_arr grid.transpose
+
+found_galaxies = []
+grid.each_with_index do |row, r|
+  row.each_with_index do |char, c|
+    next unless char == '#'
+
+    found_galaxies.each do |galaxy|
+      res += (row_offset[r] - galaxy[:x]).abs + (col_offset[c] - galaxy[:y]).abs
+    end
+
+    found_galaxies << {
+      x: row_offset[r],
+      y: col_offset[c]
+    }
+  end
+end
+
+puts res

2023/day11/p2.rb

@@ -0,0 +1,48 @@
+# frozen_string_literal: true
+
+# This is actually identical to p1, except for the offset of + 1_000_000 which was previously + 2
+
+def build_space_arr(grid)
+  offset = []
+  grid.each_with_index do |row, i|
+    offset << if row.include? '#'
+                if offset.empty?
+                  0
+                else
+                  offset[i - 1] + 1
+                end
+              elsif offset.empty?
+                1
+              else
+                offset[i - 1] + 1_000_000
+              end
+  end
+  offset
+end
+
+res = 0
+grid = []
+File.foreach('./2023/day11/data') do |line|
+  grid << line.strip.split('')
+end
+
+row_offset = build_space_arr grid
+col_offset = build_space_arr grid.transpose
+
+found_galaxies = []
+grid.each_with_index do |row, r|
+  row.each_with_index do |char, c|
+    next unless char == '#'
+
+    found_galaxies.each do |galaxy|
+      res += (row_offset[r] - galaxy[:x]).abs + (col_offset[c] - galaxy[:y]).abs
+    end
+
+    found_galaxies << {
+      x: row_offset[r],
+      y: col_offset[c]
+    }
+  end
+end
+
+puts res