AdventOfCode-2020/day7.cr

46 lines
863 B
Crystal

require "advent"
INPUT = input(2020, 7).lines.map(&.chomp).map do |s|
data = s.match(/^([a-z ]+) bags contain (.*).$/).not_nil!
contents = data[2].split(", ").compact_map do |s|
s.match(/(\d+) (.*) bags?/).try { |m| {m[1].to_i32, m[2]} }
end
{data[1], contents}
end
def build_graph(input)
gr = Graph(String).new
seen = Set(String).new
input.each do |i|
seen << i[0]
i[1].each do |to|
n, m = to
gr.add_edge(i[0], m, n)
end
end
{seen, gr}
end
def part1
seen, gr = build_graph(INPUT)
seen.count do |s|
gr.find_path(s, "shiny gold") && s != "shiny gold"
end
end
def count_bags(gr, current)
return 1 unless es = gr.@edges[current]?
1 + es.sum do |e|
t, k = e
k * count_bags(gr, t)
end
end
def part2
seen, gr = build_graph(INPUT)
count_bags(gr, "shiny gold") - 1
end
puts part1
puts part2