191. Number of 1 Bits

Problem:

Write a function that takes an unsigned integer and returns the number of ’1' bits it has (also known as the Hamming weight).

For example, the 32-bit integer ’11' has binary representation 00000000000000000000000000001011, so the function should return 3.

Analysis:

To determine ith bit in n is 1: 1 & (n >> i)

Solution:

public class Solution {
    // you need to treat n as an unsigned value
    public int hammingWeight(int n) {
        int count = 0;
        for (int i = 0; i < 32; i++) {
            count += (1 & (n >> i));
        }
        return count;
    }
}