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day 6 part 2 Use rotate_left

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Bill Thiede 2021-12-06 18:06:13 -08:00
parent 6acaaf8b7a
commit 60b77d5d3d
1 changed files with 4 additions and 10 deletions
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14
2021/src/day6.rs
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@ -88,16 +88,10 @@ fn part2(input: &str) -> Result<usize> {
.into_iter() .into_iter()
.for_each(|n| counts[n] += 1); .for_each(|n| counts[n] += 1);
for _ in 0..256 { for _ in 0..256 {
let mut tmp = [0; 9]; let ready = counts[0];
for i in 0..9 { counts.rotate_left(1);
if i == 0 { counts[6] += ready;
tmp[6] += counts[0]; counts[8] = ready;
tmp[8] += counts[0];
} else {
tmp[i - 1] += counts[i];
}
}
counts = tmp;
} }
Ok(counts.iter().sum()) Ok(counts.iter().sum())
} }