advent-of-code-9.rs

advent-of-code-9.rs

fn defrag_disk(sectors: &mut [Option<u32>]) -> Option<()> {
    let mut sectors = sectors;
    loop {
        // Find the first Empty sector
        let left_idx = sectors.iter().position(|s| s.is_none())?;

        // Find the last Full sector after the left_idx
        let right_idx = sectors[left_idx + 1..].iter().rposition(|s| s.is_some())? + left_idx + 1;

        // Swap the Empty and Full sectors
        sectors.swap(left_idx, right_idx);

        // Focus on the remaining unsorted range
        sectors = &mut sectors[left_idx + 1..right_idx];
    }
}

fn main() {
    let disk_map_str = "2333133121414131402";
    let disk_map: Vec<u32> = disk_map_str
        .chars()
        .map(|c| c.to_digit(10).unwrap())
        .collect();

    let disk_capacity: u32 = disk_map.iter().sum();
    let mut disk = Vec::with_capacity(disk_capacity.try_into().unwrap());

    let mut id = 0u32;
    for (idx, num) in disk_map.into_iter().enumerate() {
        let val = if idx % 2 == 0 {
            let v = Some(id);
            id += 1;
            v
        } else {
            None
        };

        for _ in 0..num {
            disk.push(val);
        }
    }

    defrag_disk(&mut disk);
    println!("{:?}", disk);
}