extern crate itertools;

use itertools::Itertools;

fn get_pins(observed: &str) -> Vec<String> {
    let combos = vec![
        vec![0, 8],
        vec![1, 2, 4],
        vec![2, 1, 3, 5],
        vec![3, 2, 6],
        vec![4, 1, 5, 7],
        vec![5, 2, 4, 6, 8],
        vec![6, 3, 5, 9],
        vec![7, 4, 8],
        vec![8, 0, 5, 9, 7],
        vec![9, 8, 6],
        vec![0, 8],
    ];
    let digits: Vec<_> = observed.chars().map(|c| c.to_digit(10).unwrap()).collect();
    let mut possible = vec![];
    for n in digits {
        possible.push(&combos[n as usize]);
    }
    let mut ret: Vec<String> = possible[0].iter().map(|x| x.to_string()).collect();
    for p in 1..possible.len() {
        let r: Vec<_> = ret
            .clone()
            .iter()
            .cartesian_product(possible[p].iter())
            .fold(vec![], |mut vec, (ref a, ref b)| {
                vec.push(format!("{}{}", a, b));
                vec
            });
        ret = r;
    }
    ret
}

#[test]
fn length_test() {
    let v = vec![
        ("8", vec!["5", "7", "8", "9", "0"]),
        (
            "11",
            vec!["11", "22", "44", "12", "21", "14", "41", "24", "42"],
        ),
        (
            "369",
            vec![
                "339", "366", "399", "658", "636", "258", "268", "669", "668", "266", "369", "398",
                "256", "296", "259", "368", "638", "396", "238", "356", "659", "639", "666", "359",
                "336", "299", "338", "696", "269", "358", "656", "698", "699", "298", "236", "239",
            ],
        ),
    ];
    for (num, exp) in v {
        assert_eq!(get_pins(num).len(), exp.len())
    }
}