sharparam.com
Code for the Advent of Code event
aoc
advent-of-code
Add Ruby solution for 2024 day 16
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src/2024/16/solve.rb
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src/2024/16/solve.rb
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#!/usr/bin/env ruby
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# frozen_string_literal: true
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require 'bundler/setup'
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require 'aoc/point'
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Point = AoC::Point2
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MAZE = ARGF.readlines.flat_map.with_index { |line, y|
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line.chomp.chars.map.with_index { |cell, x|
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[Point[x, y], cell]
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}
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}.to_h
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START = MAZE.find { |p, c| c == ?S }[0]
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GOAL = MAZE.find { |p, c| c == ?E }[0]
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DIRS = [
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Point[1, 0], # Right
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Point[0, 1], # Down
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Point[-1, 0], # Left
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Point[0, -1] # Up
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].freeze
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def display(path)
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$width ||= MAZE.keys.map(&:x).max + 1
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$height ||= MAZE.keys.map(&:y).max + 1
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$height.times do |y|
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$width.times do |x|
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p = Point[x, y]
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c = MAZE[p]
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if c == ?. && path.include?(p)
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print 'O'
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else
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print c
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end
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end
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puts
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end
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end
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def dfs2
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stack = [[START, Point[1, 0], Set.new, 0, [START, GOAL]]]
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min_cost = Float::INFINITY
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pos_mins = Hash.new Float::INFINITY
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paths = Hash.new { |h, k| h[k] = [] }
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until stack.empty?
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pos, dir, vis, cost, path = stack.pop
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next if cost > min_cost
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next if cost > pos_mins[pos] + 1000
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if pos == GOAL
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paths[cost] << path
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min_cost = cost if cost < min_cost
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next
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end
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pos_mins[pos] = cost if cost < pos_mins[pos]
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vis.add pos
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path << pos
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DIRS.each do |new_dir|
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new_pos = pos + new_dir
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if !vis.include?(new_pos) && MAZE[new_pos] != ?#
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turn_cost = new_dir == dir ? 0 : 1000
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stack.push [new_pos, new_dir, vis.dup, cost + turn_cost + 1, path.dup]
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end
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end
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end
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[min_cost, Set.new(paths[min_cost].flatten)]
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end
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part1, paths = dfs2
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# display(paths)
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puts part1
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puts paths.size