Number of 1 Bits

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.

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++) {
      if ((n & 1) != 0)
        count++;
      n >>>= 1;
    }
    return count;
  }
}