swap two digits without use third

swap.rs

fn main() {
    let mut x = 2;
    let mut y = 1;

    println!("before x {} y {}", x, y); // before x 2 y 1
    
    if x != y {
        x = x ^ y;
        y = x ^ y;
        x = x ^ y;
    }
        
    println!("after x {} y {}", x, y); // after x 1 y 2
}