AdventOfCode-2020/day22.cr

67 lines
1.3 KiB
Crystal

require "advent"
first, second = input(2020, 22).split("\n\n")
first = first.lines[1..].map &.to_i32
second = second.lines[1..].map &.to_i32
class Array(T)
def pop_left
delete_at(0)
end
def score
total = 0
s = size
each_with_index do |n, i|
total += n * (s - i)
end
total
end
end
def no_rec(deck1, deck2)
while !deck1.empty? && !deck2.empty?
f, s = deck1.delete_at(0), deck2.delete_at(0)
if f > s
deck1 << f << s
else
deck2 << s << f
end
end
return !deck1.empty?
end
def rec(deck1, deck2)
seen = Set({Int32, Int32}).new
while !deck1.empty? && !deck2.empty?
key = {deck1.score, deck2.score}
return true if seen.includes?(key)
seen << key
f = deck1.delete_at(0)
s = deck2.delete_at(0)
p1wins = (f <= deck1.size) && (s <= deck2.size) ? rec(deck1[0..f-1], deck2[0..s-1]) : f > s
if p1wins
deck1 << f << s
else
deck2 << s << f
end
end
return !deck1.empty?
end
def run(first, second, proc)
((proc.call(first, second)) ? first : second).score
end
def part1(input)
run(input[0], input[1], ->no_rec(Array(Int32), Array(Int32)))
end
def part2(input)
run(input[0], input[1], ->rec(Array(Int32), Array(Int32)))
end
puts part1({first, second}.clone)
puts part2({first, second}.clone)