96 lines
2.2 KiB
Rust
96 lines
2.2 KiB
Rust
#![feature(test)]
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extern crate test;
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const INPUTS: [&'static str; 2] = [
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include_str!("../inputs/day3.sample.txt"),
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include_str!("../inputs/day3.txt"),
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];
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fn cmds(input: &'static str) -> Vec<u64> {
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input
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.lines()
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.filter(|&x| !x.is_empty())
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.map(|x| u64::from_str_radix(x, 2).unwrap())
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.collect()
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}
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fn solution<const MAX_LENGTH: usize>(levels: Vec<u64>) -> u64 {
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let oxygen_gen_rating = filter_candidates::<MAX_LENGTH>(levels.clone(), true);
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let co2_scrub_rating = filter_candidates::<MAX_LENGTH>(levels, false);
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oxygen_gen_rating * co2_scrub_rating
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}
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fn filter_candidates<const MAX_LENGTH: usize>(mut levels: Vec<u64>, dominant: bool) -> u64 {
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let mut i = 0;
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while levels.len() > 1 {
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let count = count_bits::<MAX_LENGTH>(&levels, dominant);
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let leading = count & (1 << (MAX_LENGTH - i - 1));
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levels = levels
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.into_iter()
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.filter(|&x| {
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let pos = x & (1 << (MAX_LENGTH - i - 1));
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return pos == leading;
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})
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.collect();
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i += 1;
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}
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levels[0]
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}
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fn count_bits<const MAX_LENGTH: usize>(levels: &[u64], dominant: bool) -> u64 {
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let n = levels.len();
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let mut count = [0; MAX_LENGTH];
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let mut mask = 0;
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for &level in levels.iter() {
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for i in 0..MAX_LENGTH {
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let c = level & (1 << (MAX_LENGTH - i - 1));
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if c != 0 {
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count[i as usize] += 1;
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}
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}
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}
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for (i, c) in count.into_iter().enumerate() {
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if c >= n - c {
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mask |= 1 << (MAX_LENGTH - i - 1);
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}
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}
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if dominant {
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mask
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} else {
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!mask
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}
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}
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fn main() {
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let moves = cmds(INPUTS[0]);
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let count = solution::<5>(moves);
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println!("Result {}", count);
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let moves = cmds(INPUTS[1]);
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let count = solution::<12>(moves);
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println!("Result {}", count);
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}
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#[bench]
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fn solution_bench(b: &mut test::Bencher) {
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let moves = cmds(INPUTS[1]);
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b.iter(|| {
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let v = solution::<12>(moves.clone());
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test::black_box(v);
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})
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}
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#[test]
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fn solution_test() {
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assert_eq!(solution::<5>(cmds(INPUTS[0])), 230);
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assert_eq!(solution::<12>(cmds(INPUTS[1])), 4406844);
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}
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