Solution to riteangle problem

main.rs

use itertools::Itertools;
use std::time::Instant;

fn main() {
    time("elegant", maybe_more_elegant);
    time("bf", bruteforce);
}

fn time(name: &'static str, method: impl Fn()) {
    let start = Instant::now();
    method();
    let el = start.elapsed();

    println!("{name} took {el:?}");
}

fn maybe_more_elegant() {
    let sum: i32 = (0..=9).permutations(10).map(|list| {
        let [one_10, one_1, two_10, two_1, three_10, three_1, four_10, four_1, five_10, five_1] = list.as_slice() else {
            panic!()
        };

        let one = one_10 * 10 + one_1;
        let two = two_10 * 10 + two_1;
        let three = three_10 * 10 + three_1;
        let four = four_10 * 10 + four_1;
        let five = five_10 * 10 + five_1;

        [one, two, three, four, five]
    }).
        filter(|[one, two, three, four, five]| {
        let cd = two - one;
        if cd < 0 {
            false
        } else {
            (cd == three - two) && (cd == four - three) && (cd == five - four)
        }
    }).flatten().sum();

    println!("{sum}");
}

fn bruteforce() {
    let mut sum: i32 = 0;

    let numbers = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9].to_vec();
    for one_10 in numbers.clone() {
        let mut left = numbers.clone();
        left.retain(|x| *x != one_10);
        for one_1 in left.clone() {
            let mut left = left.clone();
            left.retain(|x| *x != one_1);
            let one = one_10 * 10 + one_1;

            for two_10 in left.clone() {
                let mut left = left.clone();
                left.retain(|x| *x != two_10);
                for two_1 in left.clone() {
                    let mut left = left.clone();
                    left.retain(|x| *x != two_1);
                    let two = two_10 * 10 + two_1;

                    let cd = two - one;
                    if cd < 0 {
                        continue;
                    }

                    for three_10 in left.clone() {
                        let mut left = left.clone();
                        left.retain(|x| *x != three_10);
                        for three_1 in left.clone() {
                            let mut left = left.clone();
                            left.retain(|x| *x != three_1);
                            let three = three_10 * 10 + three_1;

                            if three - two != cd {
                                continue;
                            }

                            for four_10 in left.clone() {
                                let mut left = left.clone();
                                left.retain(|x| *x != four_10);
                                for four_1 in left.clone() {
                                    let mut left = left.clone();
                                    left.retain(|x| *x != four_1);
                                    let four = four_10 * 10 + four_1;

                                    if four - three != cd {
                                        continue;
                                    }

                                    let first_five = left[0] * 10 + left[1];
                                    if first_five - four == cd {
                                        sum += one + two + three + four + first_five;
                                    }

                                    let second_five = left[1] * 10 + left[0];
                                    if second_five - four == cd {
                                        sum += one + two + three + four + second_five;
                                    }
                                }
                            }
                        }
                    }
                }
            }
        }
    }

    println!("{sum}")
}