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Use Vec::retain for day 3 

The performance issues I reported have since been fixed. Rejoice.
This commit is contained in:
kageru 2021-12-17 22:08:31 +01:00
parent 95e4a6f8cc
commit 79ab35a23e
Signed by: kageru
GPG Key ID: 8282A2BEA4ADA3D2
1 changed files with 2 additions and 6 deletions
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8
2021/src/bin/day03.rs
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@ -38,13 +38,9 @@ fn part2(parsed: &Parsed, bits: usize) -> usize {
for i in (0..bits).rev() {
let gamma = most_common_at(&matching_gamma, i);
let epsilon = !most_common_at(&matching_epsilon, i);
// TODO: Find out why retain is significantly slower than filter().collect()
// Update: Let’s see what the maintainers say: https://github.com/rust-lang/rust/issues/91497
// matching_gamma.retain(|&n| bit_at(n, i) == gamma);
matching_gamma = matching_gamma.into_iter().filter(|&n| bit_at(n, i) == gamma).collect();
matching_gamma.retain(|&n| bit_at(n, i) == gamma);
if matching_epsilon.len() > 1 {
// matching_epsilon.retain(|&n| bit_at(n, i) == epsilon);
matching_epsilon = matching_epsilon.into_iter().filter(|&n| bit_at(n, i) == epsilon).collect();
matching_epsilon.retain(|&n| bit_at(n, i) == epsilon);
}
}
debug_assert_eq!(matching_gamma.len(), 1);