Finding trailing 0s in a binary number

Question

How to find number of trailing 0s in a binary number?Based on K&R bitcount example of finding 1s in a binary number i modified it a bit to find the trailing 0s.

Answer 1

We can easily get it using bit operations, we don't need to go through all the bits. Pseudo code:

int bitcount(unsigned x) {
    int xor = x ^ (x-1); // this will have (1 + #trailing 0s) trailing 1s
    return log(i & xor); // i & xor will have only one bit 1 and its log should give the exact number of zeroes
}