src/2021/7/mod.rs


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pub fn part1() -> anyhow::Result<i64> {
    let crabs: Vec<_> = data_ints!(b',')?.collect();
    Ok((0..=crabs.iter().copied().max().unwrap())
        .map(|start| {
            crabs.iter().copied().map(|crab| (crab - start).abs()).sum()
        })
        .min()
        .unwrap())
}

pub fn part2() -> anyhow::Result<i64> {
    let crabs: Vec<_> = data_ints!(b',')?.collect();
    Ok((0..=crabs.iter().copied().max().unwrap())
        .map(|start| {
            crabs
                .iter()
                .copied()
                .map(|crab| {
                    let diff = (crab - start).abs();
                    diff * (diff + 1) / 2
                })
                .sum()
        })
        .min()
        .unwrap())
}

#[test]
fn test() {
    assert_eq!(part1().unwrap(), 333755);
    assert_eq!(part2().unwrap(), 94017638);
}