91 lines
2.2 KiB
Rust
91 lines
2.2 KiB
Rust
use aoc_runner_derive::{aoc, aoc_generator};
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use memoize::memoize;
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use misc::POW10;
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#[aoc_generator(day3)]
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fn parse(input: &str) -> Vec<Vec<u8>> {
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input
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.lines()
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.map(|bank| bank.bytes().map(|c| c - b'0').collect())
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.collect()
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}
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#[memoize]
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fn max_joltage(bank: Vec<u8>, n: usize) -> u64 {
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if n == 1 {
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return *bank.iter().max().unwrap() as u64;
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}
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(0..bank.len() - n + 1)
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.map(|start| {
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bank[start] as u64 * POW10[n - 1] + max_joltage(bank[start + 1..].to_vec(), n - 1)
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})
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.max()
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.unwrap()
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}
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fn max_joltage_2(bank: &[u8], n: usize) -> u64 {
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if n == 1 {
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return *bank.iter().max().unwrap() as u64;
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}
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let choices = &bank[..bank.len() - (n - 1)];
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// Note: can't use position_max() here since it returns the _last_ instance and we need the _first_.
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// get the max, then find the first instance of that value. There is definitely a one-pass solution.
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let max = choices.iter().max().unwrap();
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let choice = choices.iter().position(|n| max == n).unwrap();
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let rest = &bank[choice + 1..];
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bank[choice] as u64 * POW10[n - 1] + max_joltage_2(rest, n - 1)
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}
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#[aoc(day3, part1, Brute)]
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fn part1(input: &[Vec<u8>]) -> u64 {
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input.iter().map(|bank| max_joltage(bank.clone(), 2)).sum()
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}
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#[aoc(day3, part2, Brute)]
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fn part2(input: &[Vec<u8>]) -> u64 {
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input.iter().map(|bank| max_joltage(bank.clone(), 12)).sum()
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}
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#[aoc(day3, part1, Smart)]
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fn part1_smart(input: &[Vec<u8>]) -> u64 {
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input.iter().map(|bank| max_joltage_2(bank, 2)).sum()
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}
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#[aoc(day3, part2, Smart)]
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fn part2_smart(input: &[Vec<u8>]) -> u64 {
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input.iter().map(|bank| max_joltage_2(bank, 12)).sum()
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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const EXAMPLE: &str = "987654321111111
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811111111111119
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234234234234278
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818181911112111";
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#[test]
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fn part1_example() {
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assert_eq!(part1(&parse(EXAMPLE)), 357);
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}
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#[test]
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fn part2_example() {
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assert_eq!(part2(&parse(EXAMPLE)), 3121910778619);
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}
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#[test]
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fn part1_smart_example() {
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assert_eq!(part1_smart(&parse(EXAMPLE)), 357);
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}
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#[test]
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fn part2_smart_example() {
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assert_eq!(part2_smart(&parse(EXAMPLE)), 3121910778619);
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}
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}
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