38 lines
828 B
Crystal
38 lines
828 B
Crystal
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require "advent"
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INPUT = input(2020, 10).lines.map(&.to_i32).sort!
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def part1(input)
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diff_1 = 0
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diff_3 = 0
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curr = 0
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input << (input.max + 3)
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input.each do |i|
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diff_1 += 1 if (i - curr) == 1
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diff_3 += 1 if (i - curr) == 3
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curr = i
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end
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puts diff_1 * diff_3
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end
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def count_ways(input, prev, index, mem, indent = 0)
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if m = mem[{prev, index}]?
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return m
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end
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return 0_i64 if input[index] - prev > 3 || index >= input.size
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return 1_i64 if index == input.size - 1
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total = count_ways(input, input[index], index+1, mem, indent + 1)
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total += count_ways(input, prev, index+1, mem, indent + 1)
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mem[{prev, index}] = total
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return total
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end
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def part2(input)
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input << (input.max + 3)
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count_ways(input, 0, 0, {} of {Int32, Int32} => Int64)
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end
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puts part1(INPUT.clone)
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puts part2(INPUT.clone)
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