Add day 17

Gemfile

@@ -0,0 +1,5 @@
+# frozen_string_literal: true
+
+source "https://rubygems.org"
+
+gem "algorithms"

Gemfile.lock

@@ -0,0 +1,14 @@
+GEM
+  remote: https://rubygems.org/
+  specs:
+    algorithms (1.0.1)
+
+PLATFORMS
+  arm64-darwin-23
+  ruby
+
+DEPENDENCIES
+  algorithms
+
+BUNDLED WITH
+   2.5.1

README.md

@@ -16,3 +16,4 @@
 1. [Day 14](./src/d14)
 1. [Day 15](./src/d15)
 1. [Day 16](./src/d16)
+1. [Day 17](./src/d17)

src/d17/d17_part_one.rb

@@ -0,0 +1,81 @@
+# frozen_string_literal: true
+
+require "algorithms"
+
+def day17_part_one(input)
+  # Parse input
+  grid = input.map { |l| l.split("").map(&:to_i) }
+
+  seen = Set.new
+  pqueue = Containers::PriorityQueue.new { |a, b| (a <=> b) == -1 } # min has priority
+
+  min_heat_loss = 0
+  while min_heat_loss.zero?
+    priority = pqueue.pop || [0, 0, 0, 0, 0, 0]
+
+    heat_loss, row, col, drow, dcol, moves = priority
+
+    # Destination reached
+    if row == grid.length - 1 && col == grid[0].length - 1
+      min_heat_loss = heat_loss
+      break
+    end
+
+    # Skip if already seen
+    next if seen.include?([row, col, drow, dcol, moves])
+
+    seen << [row, col, drow, dcol, moves]
+
+    # Move to next block
+    if moves < 3 && [drow, dcol] != [0, 0]
+      nrow = row + drow
+      ncol = col + dcol
+
+      if nrow >= 0 && nrow < grid.length && ncol >= 0 && ncol < grid[0].length
+        new_heat_loss = heat_loss + grid[nrow][ncol]
+        pqueue.push([new_heat_loss, nrow, ncol, drow, dcol, moves + 1], priority)
+      end
+    end
+
+    # Move in all possible directions
+    [[0, 1], [1, 0], [0, -1], [-1, 0]].each do |ndrow, ndcol|
+      next unless [ndrow, ndcol] != [drow, dcol] && [ndrow, ndcol] != [-drow, -dcol]
+
+      nrow = row + ndrow
+      ncol = col + ndcol
+
+      if nrow >= 0 && nrow < grid.length && ncol >= 0 && ncol < grid[0].length
+        new_heat_loss = heat_loss + grid[nrow][ncol]
+        pqueue.push([new_heat_loss, nrow, ncol, ndrow, ndcol, 1], priority)
+      end
+    end
+  end
+
+  min_heat_loss
+end
+
+test = <<~INPUT
+  2413432311323
+  3215453535623
+  3255245654254
+  3446585845452
+  4546657867536
+  1438598798454
+  4457876987766
+  3637877979653
+  4654967986887
+  4564679986453
+  1224686865563
+  2546548887735
+  4322674655533
+INPUT
+  .split(/\n/)
+
+pp day17_part_one(test)
+
+# Large puzzle input
+file = File.open("d17.txt")
+file_data = file.readlines.map(&:chomp)
+file.close
+
+pp day17_part_one(file_data)

src/d17/d17_part_two.rb

@@ -0,0 +1,83 @@
+# frozen_string_literal: true
+
+require "algorithms"
+
+def day17_part_two(input)
+  # Parse input
+  grid = input.map { |l| l.split("").map(&:to_i) }
+
+  seen = Set.new
+  pqueue = Containers::PriorityQueue.new { |a, b| (a <=> b) == -1 } # min has priority
+
+  min_heat_loss = 0
+  while min_heat_loss.zero?
+    priority = pqueue.pop || [0, 0, 0, 0, 0, 0]
+
+    heat_loss, row, col, drow, dcol, moves = priority
+
+    # Destination reached
+    if row == grid.length - 1 && col == grid[0].length - 1 && n >= 4
+      min_heat_loss = heat_loss
+      break
+    end
+
+    # Skip if already seen
+    next if seen.include?([row, col, drow, dcol, moves])
+
+    seen << [row, col, drow, dcol, moves]
+
+    # Move to next block
+    if moves < 10 && [drow, dcol] != [0, 0]
+      nrow = row + drow
+      ncol = col + dcol
+
+      if nrow >= 0 && nrow < grid.length && ncol >= 0 && ncol < grid[0].length
+        new_heat_loss = heat_loss + grid[nrow][ncol]
+        pqueue.push([new_heat_loss, nrow, ncol, drow, dcol, moves + 1], priority)
+      end
+    end
+
+    # Move in all possible directions only if the movesber of moves is less than 4
+    next unless moves >= 4 || [drow, dcol] == [0, 0]
+
+    [[0, 1], [1, 0], [0, -1], [-1, 0]].each do |ndrow, ndcol|
+      next unless [ndrow, ndcol] != [drow, dcol] && [ndrow, ndcol] != [-drow, -dcol]
+
+      nrow = row + ndrow
+      ncol = col + ndcol
+
+      if nrow >= 0 && nrow < grid.length && ncol >= 0 && ncol < grid[0].length
+        new_heat_loss = heat_loss + grid[nrow][ncol]
+        pqueue.push([new_heat_loss, nrow, ncol, ndrow, ndcol, 1], priority)
+      end
+    end
+  end
+
+  min_heat_loss
+end
+
+test = <<~INPUT
+  2413432311323
+  3215453535623
+  3255245654254
+  3446585845452
+  4546657867536
+  1438598798454
+  4457876987766
+  3637877979653
+  4654967986887
+  4564679986453
+  1224686865563
+  2546548887735
+  4322674655533
+INPUT
+  .split(/\n/)
+
+pp day17_part_two(test)
+
+# Large puzzle input
+file = File.open("d17.txt")
+file_data = file.readlines.map(&:chomp)
+file.close
+
+pp day17_part_two(file_data)