191. Number of 1 Bits

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

Example 1:

Input: 00000000000000000000000000001011
Output: 3
Explanation: The input binary string 00000000000000000000000000001011 has a total of three '1' bits.

Example 2:

Input: 00000000000000000000000010000000
Output: 1
Explanation: The input binary string 00000000000000000000000010000000 has a total of one '1' bit.

Example 3:

Input: 11111111111111111111111111111101
Output: 31
Explanation: The input binary string 11111111111111111111111111111101 has a total of thirty one '1' bits.

public int hammingWeight2(int n) {
    int result = 0;
    for(int i = 0; i < 32; i++) {
        result += ((n >>> i) & 1);
    }
    return result;
}

public int hammingWeight(int n) {
    int result = 0;
    while(n != 0) {
        n &= (n-1);
        result++;
    }
    return result;
}