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