191. Number of 1 Bits --E

 Q:

Write a function that takes the binary representation of a positive integer and returns the number of 

set bits

 it has (also known as the Hamming weight).

 

Example 1:

Input: n = 11

Output: 3

Explanation:

The input binary string 1011 has a total of three set bits.

Example 2:

Input: n = 128

Output: 1

Explanation:

The input binary string 10000000 has a total of one set bit.

Example 3:

Input: n = 2147483645

Output: 30

Explanation:

The input binary string 1111111111111111111111111111101 has a total of thirty set bits.

 

Constraints:

• 1 <= n <= 231 - 1

A:

class Solution {

public:

int hammingWeight(int n) {

int res = 0;

while(n){

n = n & (n-1);

++res;

}

return res;

}

};