day_07.rs

use common::{solution, Answer};

solution!("The Treachery of Whales", 7);

fn part_a(input: &str) -> Answer {
    let data = parse_crabs(input);

    let min = data.iter().min().unwrap();
    let max = data.iter().max().unwrap();

    let mut this_min = u32::MAX;
    for i in *min..=*max {
        let cost = move_crabs(&data, i);
        if cost < this_min {
            this_min = cost;
        }
    }

    this_min.into()
}

fn part_b(input: &str) -> Answer {
    let data = parse_crabs(input);

    let min = data.iter().min().unwrap();
    let max = data.iter().max().unwrap();

    let mut this_min = u32::MAX;
    for i in *min..=*max {
        let cost = move_crabs_b(&data, i);
        if cost < this_min {
            this_min = cost;
        }
    }

    this_min.into()
}

fn parse_crabs(inp: &str) -> Vec<u32> {
    inp.lines()
        .next()
        .unwrap()
        .split(',')
        .map(|x| x.parse().unwrap())
        .collect::<Vec<u32>>()
}

fn move_crabs(crabs: &[u32], to: u32) -> u32 {
    let mut cost = 0;
    for i in crabs {
        cost += (*i as i32 - to as i32).abs();
    }

    cost as u32
}

fn move_crabs_b(crabs: &[u32], to: u32) -> u32 {
    let mut cost = 0;
    for crab in crabs {
        cost += (0..=(*crab as i32 - to as i32).abs()).sum::<i32>();
    }

    cost as u32
}