Function aoc::year2021::day21::part2

pub fn part2(input: &((usize, usize), (usize, usize))) -> usize

Memoization is the key to solving part two in a reasonable time. For each possible starting universe we record the number of winning and losing recursive universes so that we can re-use the result and avoid uneccessary calculations.

Each player can be in position 1 to 10 and can have a score from 0 to 20 (as a score of 21 ends the game). This is a total of (10 * 21) ^ 2 = 44100 possible states. For speed this can fit in an array with perfect hashing, instead of using a slower HashMap.