Mercurial > repos > other > adventofcode2023
view day6.rb @ 39:0e17e4bd97a9 default tip
Rewrite as four-dimensional route finding
The grid isn't just a 2D grid. The constraints make it 4D:
* X
* Y
* Last direction
* Number of steps in that direction
By tracking all four dimensions, we can find the shortest route
for _all_ combinations of the constraint. Previously, we were dropping
routes that were currently longer but ended up shorter because
they could take subsequent steps that other routes couldn't.
author | IBBoard <dev@ibboard.co.uk> |
---|---|
date | Sun, 22 Sep 2024 11:30:53 +0100 |
parents | 51e5f26dc81e |
children |
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#! /usr/bin/env ruby if ARGV.length != 1 abort("Incorrect arguments - needs input file") elsif not File.exist? (ARGV[0]) abort("File #{ARGV[0]} did not exist") end file = ARGV[0] times, distances = File.open(file, "r").each_line(chomp: true).map {|v| puts v; puts v.split(":"); v.split(":")[1].split(" ").map(&:to_i)} events = times.zip(distances) product = events.map do |event| mid = (event[0].to_f / 2).floor first_success = (1..mid).bsearch {|i| (event[0] - i) * i > event[1]} num_success = (mid - first_success + 1) * 2 event[0].odd? ? num_success : num_success - 1 end.reduce(:*) puts product