Hamming Weight

hamming_weight.rs

fn countOnes(x: usize) -> usize {
    let mut c = 0;
    let mut x = x;
    c = (x & 0x55555555) + ((x >> 1) & 0x55555555);
    c = (c & 0x33333333) + ((c >> 2) & 0x33333333);
    c = (c & 0x0f0f0f0f) + ((c >> 4) & 0x0f0f0f0f);
    c = (c & 0x00ff00ff) + ((c >> 8) & 0x00ff00ff);
    c = (c & 0x0000ffff) + ((c >> 16) & 0x0000ffff);
    return c;
}