aoc 2022 day04

day04.rs

fn parse_line(line: &str) -> (i32, i32, i32, i32) {
    let mut split = line.split(",");
    let left = split.next().unwrap();
    let mut ls = left.split("-");
    let left_from: i32 = ls.next().unwrap().parse().unwrap();
    let left_to: i32 = ls.next().unwrap().parse().unwrap();
    let right = split.next().unwrap();
    let mut rs = right.split("-");
    let right_from: i32 = rs.next().unwrap().parse().unwrap();
    let right_to: i32 = rs.next().unwrap().parse().unwrap();
    (left_from, left_to, right_from, right_to)
}

// check if left fully contains right
fn fully_contains(left_from: i32, left_to: i32, right_from: i32, right_to: i32) -> bool {
    left_from <= right_from && left_to >= right_to
}

fn overlap_at_all(left_from: i32, left_to: i32, right_from: i32, right_to: i32) -> bool {
    // there are only 2 cases where they don't overlap
    // one whole interval is less than the start of the other
    !((left_from < right_from && left_to < right_from)
        || (right_from < left_from && right_to < left_from))
}

fn main() {
    let input = include_str!("day04_input.txt");

    let mut num_fully_contained = 0;
    let mut num_overlap = 0;
    for line in input.split("\n") {
        let (left_from, left_to, right_from, right_to) = parse_line(line);
        if fully_contains(left_from, left_to, right_from, right_to)
            || fully_contains(right_from, right_to, left_from, left_to)
        {
            num_fully_contained += 1;
        }
        if overlap_at_all(left_from, left_to, right_from, right_to) {
            num_overlap += 1;
        }
    }
    println!("num fully contained {num_fully_contained}");
    println!("num overlap {num_overlap}");
}