most trivial implementation of quick_sort I could come up with

quicksort.rs

fn main() {
    let mut arr = vec![
        8,
        4,
        1,
        10,
        0,
        3,
        4,
        3,
        9
    ];
    quick_sort(&mut arr);
    for x in arr {
        println!("{}", x);
    }
}

fn quick_sort_helper(input: &mut Vec<i64>, f_index: usize, l_index: usize) {
    let mut i = f_index;
    let mut j = l_index;
    let mut l = 1;
    let mut r = 0;
    loop {
        if input[i] > input[j] {
            input.swap(i, j);
            // this makes it so each swap will start moving the opposite caret
            // until another swap occurs
            l ^= 1;
            r ^= 1;
        }
        // stop when `i` and `j` are next to each other
        if j - i == 1 {
            break;
        }
        i += l;
        j -= r;
    }
    if f_index != i {
        quick_sort_helper(input, f_index, i);
    }
    if l_index != j {
        quick_sort_helper(input, j, l_index);
    }
}

fn quick_sort(input: &mut Vec<i64>) {
    let len = input.len();
    quick_sort_helper(input, 0, len - 1);
}