Add 2024/12 rb

erikw · erikw · commit 9b272ade7f15 · 2025-10-29T21:11:47.000+01:00
diff --git a/2024/12/README.md b/2024/12/README.md
@@ -0,0 +1,12 @@
+# Advent of Code - 2024 Day 12
+Here are my solutions to this puzzle.
+
+* Problem instructions: [adventofcode.com/2024/day/12](https://adventofcode.com/2024/day/12)
+* Input: [adventofcode.com/2024/day/12/input](https://adventofcode.com/2024/day/12/input)
+
+Fetch input by exporting `$AOC_SESSION` in your shell and then:
+```bash
+curl -OJLsb session=$AOC_SESSION adventofcode.com/2024/day/12/input
+```
+
+or run `fetch_input.sh` in this directory.
diff --git a/2024/12/fetch_input.sh b/2024/12/fetch_input.sh
@@ -0,0 +1,5 @@
+#!/usr/bin/env sh
+# Make sure $AOC_SESSION is exported before running this script.
+
+curl --remote-name --remote-header-name --silent --fail -A 'https://erikw.me/contact' --cookie "session=$AOC_SESSION" "https://adventofcode.com/2024/day/12/input"
+test "$?" -eq 0 && echo "Fetched input" && exit 0 || echo "Failed to fetch input" && exit 1
diff --git a/2024/12/input1.0 b/2024/12/input1.0
@@ -0,0 +1,4 @@
+AAAA
+BBCD
+BBCC
+EEEC
diff --git a/2024/12/input1.1 b/2024/12/input1.1
@@ -0,0 +1,5 @@
+OOOOO
+OXOXO
+OOOOO
+OXOXO
+OOOOO
diff --git a/2024/12/input1.2 b/2024/12/input1.2
@@ -0,0 +1,10 @@
+RRRRIICCFF
+RRRRIICCCF
+VVRRRCCFFF
+VVRCCCJFFF
+VVVVCJJCFE
+VVIVCCJJEE
+VVIIICJJEE
+MIIIIIJJEE
+MIIISIJEEE
+MMMISSJEEE
diff --git a/2024/12/input2.0 b/2024/12/input2.0
@@ -0,0 +1,4 @@
+AAAA
+BBCD
+BBCC
+EEEC
diff --git a/2024/12/input2.1 b/2024/12/input2.1
@@ -0,0 +1,5 @@
+OOOOO
+OXOXO
+OOOOO
+OXOXO
+OOOOO
diff --git a/2024/12/input2.2 b/2024/12/input2.2
@@ -0,0 +1,5 @@
+EEEEE
+EXXXX
+EEEEE
+EXXXX
+EEEEE
diff --git a/2024/12/input2.3 b/2024/12/input2.3
@@ -0,0 +1,6 @@
+AAAAAA
+AAABBA
+AAABBA
+ABBAAA
+ABBAAA
+AAAAAA
diff --git a/2024/12/input2.4 b/2024/12/input2.4
@@ -0,0 +1,10 @@
+RRRRIICCFF
+RRRRIICCCF
+VVRRRCCFFF
+VVRCCCJFFF
+VVVVCJJCFE
+VVIVCCJJEE
+VVIIICJJEE
+MIIIIIJJEE
+MIIISIJEEE
+MMMISSJEEE
diff --git a/2024/12/instructions.url b/2024/12/instructions.url
@@ -0,0 +1,2 @@
+[InternetShortcut]
+URL=https://adventofcode.com/2024/day/12
diff --git a/2024/12/output1.0 b/2024/12/output1.0
@@ -0,0 +1 @@
+140
diff --git a/2024/12/output1.1 b/2024/12/output1.1
@@ -0,0 +1 @@
+772
diff --git a/2024/12/output1.2 b/2024/12/output1.2
@@ -0,0 +1 @@
+1930
diff --git a/2024/12/output2.0 b/2024/12/output2.0
@@ -0,0 +1 @@
+80
diff --git a/2024/12/output2.1 b/2024/12/output2.1
@@ -0,0 +1 @@
+436
diff --git a/2024/12/output2.2 b/2024/12/output2.2
@@ -0,0 +1 @@
+236
diff --git a/2024/12/output2.3 b/2024/12/output2.3
@@ -0,0 +1 @@
+368
diff --git a/2024/12/output2.4 b/2024/12/output2.4
@@ -0,0 +1 @@
+1206
diff --git a/2024/12/part1.rb b/2024/12/part1.rb
@@ -0,0 +1,58 @@
+#!/usr/bin/env ruby
+# frozen_string_literal: true
+
+NEIGHBOR_DELTAS = [
+  [-1, 0],
+  [0, 1],
+  [1, 0],
+  [0, -1]
+].freeze
+
+def neighbor_positions(pos)
+  NEIGHBOR_DELTAS.map { |dr, dc| [pos[0] + dr, pos[1] + dc] }
+end
+
+def discover_region(map, pos)
+  area = 0
+  perimeter = 0
+  region = Set.new
+  plant = map[pos]
+
+  stack = [pos]
+
+  until stack.empty?
+    pos = stack.pop
+    next if region.include?(pos) || map[pos] != plant
+
+    region << pos
+
+    area += 1
+    neighbor_positions(pos).each do |posn|
+      if map[posn] == plant
+        stack << posn
+      else
+        perimeter += 1
+      end
+    end
+  end
+
+  [area, perimeter, region]
+end
+
+map = {}
+ARGF.each_line(chomp: true).with_index do |line, row|
+  line.each_char.with_index do |plant, col|
+    map[[row, col]] = plant
+  end
+end
+
+total_price = 0
+unseen = map.keys.to_set
+until unseen.empty?
+  area, perimeter, region = discover_region(map, unseen.first)
+  unseen -= region
+  price = area * perimeter
+  total_price += price
+end
+
+puts total_price
diff --git a/2024/12/part2.rb b/2024/12/part2.rb
@@ -0,0 +1,98 @@
+#!/usr/bin/env ruby
+# frozen_string_literal: true
+
+NEIGHBOR_DELTAS = [-1, 1i, 1, -1i].freeze
+
+CORNER_DELTAS = [
+  [-1i, -1 - 1i, -1], # top left
+  [-1, -1 + 1i, 1i], # top right
+  [1i, 1 + 1i, 1], # bottom right
+  [1, 1 - 1i, -1i] # bottom left
+].freeze
+
+def neighbor_positions(pos)
+  NEIGHBOR_DELTAS.map { |d| pos + d }
+end
+
+def corner_neighbours(pos)
+  CORNER_DELTAS.map { |deltas| deltas.map { |d| pos + d } }
+end
+
+def sorted_positions(*positions)
+  positions.sort_by { |p| [p.real, p.imag] }
+end
+
+def outer_corner(region, pos, pos1, _pos2, pos3)
+  is_corner = [pos1, pos3].none? do |p|
+    region.include?(p)
+  end
+
+  pos_corner = sorted_positions(pos, pos1, pos3)
+
+  is_corner ? pos_corner : nil
+end
+
+def inner_corner(region, pos, pos1, pos2, pos3)
+  is_corner = region.include?(pos2) && region.include?(pos1) ^ region.include?(pos3)
+
+  pos_side = region.include?(pos1) ? pos1 : pos3
+  pos_corner = sorted_positions(pos, pos2, pos_side)
+
+  is_corner ? pos_corner : nil
+end
+
+def discover_region(map, pos)
+  region = Set.new
+  plant = map[pos]
+
+  stack = [pos]
+
+  until stack.empty?
+    pos = stack.pop
+    next if region.include?(pos) || map[pos] != plant
+
+    region << pos
+
+    neighbor_positions(pos).each do |posn|
+      stack << posn if map[posn] == plant
+    end
+  end
+
+  region
+end
+
+def count_sides(region)
+  corners = Set.new
+
+  region.each do |pos|
+    corner_neighbours(pos).each do |pos1, pos2, pos3|
+      pos_corner = outer_corner(region, pos, pos1, pos2, pos3) || inner_corner(region, pos, pos1, pos2, pos3)
+      corners << pos_corner if pos_corner
+    end
+  end
+
+  corners.size
+end
+
+map = {}
+ARGF.each_line(chomp: true).with_index do |line, row|
+  line.each_char.with_index do |plant, col|
+    map[Complex(row, col)] = plant
+  end
+end
+
+unseen = map.keys.to_set
+regions = []
+until unseen.empty?
+  region = discover_region(map, unseen.first)
+  unseen -= region
+  regions << region
+end
+
+total_price = regions.sum do |region|
+  area = region.size
+  sides = count_sides(region)
+  area * sides
+end
+
+puts total_price

-Original file line number
+Diff line change
@@ @@ -0,0 +1,4 @@ @@
 +AAAA
 +BBCD
 +BBCC
 +EEEC