Mercurial > repos > other > adventofcode2023
annotate day19.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> |
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date | Sun, 22 Sep 2024 11:30:53 +0100 |
parents | 5ba34a851816 |
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28
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1 #! /usr/bin/env ruby |
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2 |
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3 if ARGV.length != 1 |
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4 abort("Incorrect arguments - needs input file") |
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5 elsif not File.exist? (ARGV[0]) |
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6 abort("File #{ARGV[0]} did not exist") |
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7 end |
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8 |
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9 file = ARGV[0] |
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10 |
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11 workflows = Hash.new |
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12 Workflow = Struct.new(:name, :rules) |
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13 Rule = Struct.new(:filter, :next) |
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14 Filter = Struct.new(:field, :comparison, :value) |
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15 objects = Array.new |
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16 Object = Struct.new(:x, :m, :a, :s) |
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17 |
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18 File.open(file, "r").each_line(chomp: true) do |line| |
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19 if line == "" |
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20 next |
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21 end |
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22 bracket_pos = line.index("{") |
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23 if bracket_pos == 0 |
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24 # Parse an object |
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25 match = line.match("\{x=([0-9]+),m=([0-9]+),a=([0-9]+),s=([0-9]+)\}") |
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26 objects << Object.new(x=match[1].to_i, m=match[2].to_i, a=match[3].to_i, s=match[4].to_i) |
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27 else |
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28 # Parse a workflow |
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29 workflow_name = line[0,bracket_pos] |
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30 rules = line[(bracket_pos+1)..-2].split(",").map do |rule| |
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31 rule_parts = rule.split(":") |
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32 if rule_parts.length > 1 |
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33 rule, next_workflow = rule_parts |
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34 filter = Filter.new(rule[0].to_sym, rule[1].to_sym, rule[2..-1].to_i) |
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35 Rule.new(filter, next_workflow) |
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36 else |
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37 Rule.new(Filter.new(:a, ">".to_sym, -1), rule_parts[0]) |
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38 end |
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39 end |
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40 workflows[workflow_name] = Workflow.new(name=workflow_name, rules=rules) |
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41 end |
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42 end |
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43 |
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44 filtered_objects = objects.map do |obj| |
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45 workflow_name = "in" |
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46 while workflow_name != "R" and workflow_name != "A" |
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47 workflow = workflows[workflow_name] |
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48 workflow.rules.each do |rule| |
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49 puts rule |
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50 filter = rule.filter |
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51 if obj.public_send(filter.field).public_send(filter.comparison, filter.value) |
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52 workflow_name = rule.next |
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53 break |
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54 end |
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55 end |
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56 end |
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57 obj if workflow_name == "A" |
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58 end.reject(&:nil?) |
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59 puts "#{filtered_objects.to_a}" |
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60 puts "#{filtered_objects.reduce(0) {|accum, obj| accum + obj.x + obj.m + obj.a + obj.s}}" |