Heap's Algorithm for Permutation Generation in Rust

heapsAlgorithmForPermutationGeneration.rs

//https://en.wikipedia.org/wiki/Heap%27s_algorithm
fn main(){
    let mut array = vec![1,2,3,4];
    generate(4, &mut array);
}

fn generate(n : usize, a : &mut Vec<usize>) {
    if n == 1 {
        println!("{:?}", a);
    }
    else {
        for i in  0 .. n - 1 {
            generate(n - 1, a);

            if n % 2 == 0 {
                a.swap(i, n - 1);
            }
            else {
                a.swap(0, n - 1);
            }
        }
        generate(n - 1, a);
    }
}