73 lines
1.8 KiB
Rust
73 lines
1.8 KiB
Rust
use crate::prelude::*;
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pub type O = usize;
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pub const INPUT: &'static str = "qzyelonm";
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fn _solve (extra: u32) -> O {
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let mut candidates: M<char, Vec<usize>> = M::new();
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let mut done: Vec<usize> = vec![];
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for i in 0.. {
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let s = format!("{INPUT}{i}");
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let mut hash = md5::compute(s);
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let mut repr = format!("{:x}", hash);
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for _ in 0..extra {
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hash = md5::compute(repr);
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repr = format!("{:x}", hash);
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}
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let three = repr.chars().tuple_windows().find(|&(a, b, c)| a == b && b == c);
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if let Some((c, _, _)) = three {
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if !candidates.is_empty() {
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let five = repr.chars().tuple_windows().find(|&(a, b, c, d, e)| a == b && a == c && a == d && a == e);
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if let Some((c, _, _, _, _)) = five {
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if let Some(candidates) = candidates.get_mut(&c) {
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let pos = candidates.iter().position(|pos| pos + 1000 > i);
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if let Some(pos) = pos {
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done.extend(candidates.drain(pos..));
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candidates.clear();
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if done.len() >= 100 { // should be pretty solid, but not sure if I can prove this!
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done.sort();
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return done[63];
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}
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}
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}
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}
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}
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candidates.entry(c).or_default().push(i);
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}
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}
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0
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}
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fn _silver () -> O {
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_solve(0)
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}
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fn _gold () -> O {
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_solve(2016)
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}
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#[cfg(test)]
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mod test {
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use super::*;
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#[test]
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fn silver () {
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let ans = _silver();
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assert_eq!(ans, 15168)
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}
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#[test]
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fn gold () {
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let ans = _gold();
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assert_eq!(ans, 20864)
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}
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}
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