Day nine

9-1.rb

@@ -0,0 +1,51 @@
+#!/usr/bin/env ruby
+
+problem = 9
+input = File.read("#{problem}.input")
+#input = DATA.read
+  .chars
+  .map(&:to_i)
+
+expanded_disk = []
+
+id = 0
+type = :file
+input.each do
+  if type == :free
+    _1.times { expanded_disk << "." }
+
+    type = :file
+  else
+    _1.times { expanded_disk << id }
+    id += 1
+    type = :free
+  end
+end
+
+defragmented_disk = Array.new(expanded_disk.size)
+
+l, r = 0, expanded_disk.size - 1
+while l <= r
+  if expanded_disk[l] != "."
+    defragmented_disk[l] = expanded_disk[l]
+    l += 1
+  elsif expanded_disk[r] == "."
+    defragmented_disk[r] = expanded_disk[r]
+    r -= 1
+  else
+    defragmented_disk[l] = expanded_disk[r]
+    defragmented_disk[r] = "."
+    l += 1
+    r -= 1
+  end
+end
+
+checksum = defragmented_disk
+  .map.with_index { _1.to_i * _2.to_i }
+  .sum
+
+p checksum
+
+
+__END__
+2333133121414131402

9-2.rb

@@ -0,0 +1,75 @@
+#!/usr/bin/env ruby
+
+require "debug"
+
+problem = 9
+input = File.read("#{problem}.input")
+#input = DATA.read
+  .chars
+  .map(&:to_i)
+
+expanded_disk = []
+
+id = 0
+type = :file
+input.each do
+  if type == :free
+    _1.times { expanded_disk << "." }
+
+    type = :file
+  else
+    _1.times { expanded_disk << id }
+    id += 1
+    type = :free
+  end
+end
+
+defragmented_disk = expanded_disk.dup
+
+start = Time.now
+r = expanded_disk.size - 1
+while r > 0
+  if expanded_disk[r] == "."
+    r -= 1
+  else
+    rr = r
+    rr -= 1 while expanded_disk[rr] == expanded_disk[r]
+    space = r - rr
+
+    l = expanded_disk.index(".")
+    while l < expanded_disk.size
+      if expanded_disk[l] != "."
+        l += 1
+        next
+      end
+
+      ll = l
+      ll += 1 while defragmented_disk[ll] == "."
+      free = ll - l
+
+      if l > r
+        break
+      elsif free >= space
+        (l..(l + space - 1)).each { defragmented_disk[_1] = expanded_disk[r] }
+        ((rr + 1)..r).each { defragmented_disk[_1] = "." }
+        break
+      else
+        l = ll + 1
+      end
+    end
+
+    r = rr
+  end
+end
+finish = Time.now
+puts "Finished in #{finish - start}"
+
+checksum = defragmented_disk
+  .map.with_index { _1.to_i * _2.to_i }
+  .sum
+
+p checksum
+
+
+__END__
+2333133121414131402