day3.rs

//! [Day 3: Squares With Three Sides](https://adventofcode.com/2016/day/3)

use itertools::Itertools;

pub fn main() {
    let args = aoc::parse_args();
    args.run(solve);
}

/// # Panics
#[must_use]
pub fn solve(data: &str) -> (u32, u32) {
    (part1(data), part2(data))
}

fn parse(line: &str) -> (i32, i32, i32) {
    let (x, y, z) = line
        .split_ascii_whitespace()
        .map_while(|i| i.parse::<i32>().ok())
        .collect_tuple()
        .unwrap();
    (x, y, z)
}

/// ``part1`` counts the triangles in the input with the three sides on the same line.
fn part1(data: &str) -> u32 {
    data.lines()
        .map(|line| {
            let (x, y, z) = parse(line);
            is_triangle(x, y, z)
        })
        .sum()
}

/// ``part2`` counts the triangles in the input with the three sides on three successive lines, one triangle per column.
fn part2(data: &str) -> u32 {
    let mut triangles = 0;
    let lines = data.lines().collect::<Vec<_>>();

    for line in lines.chunks(3) {
        let (x1, y1, z1) = parse(line[0]);
        let (x2, y2, z2) = parse(line[1]);
        let (x3, y3, z3) = parse(line[2]);

        triangles += is_triangle(x1, x2, x3);
        triangles += is_triangle(y1, y2, y3);
        triangles += is_triangle(z1, z2, z3);
    }

    triangles
}

/// ``is_triangle`` returns 1 if the given sides form a triangle, 0 otherwise
fn is_triangle(x: i32, y: i32, z: i32) -> u32 {
    u32::from(x + y > z && x + z > y && y + z > x)
}

#[cfg(test)]
mod test {
    use super::*;

    #[test]
    fn test_part1() {
        assert_eq!(part1("5 10 25"), 0);
        assert_eq!(part1("5 10 10"), 1);
    }

    #[test]
    fn test_part2() {
        let data = "101 301 501
102 302 502
103 303 503
201 401 601
202 402 602
203 403 603
";
        assert_eq!(part2(data), 6);
    }
}