Number of 1 Bits

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.

 

class Solution {
public:
    int hammingWeight(uint32_t n) {
        int bits=0;
        
        while (n > 0){
            if(n & 0x1 == 1)
                bits++;
            n = n >> 1;
        }
        return bits;
    }
};
/*
int hammingWeight(uint32_t n)
{
    int res = 0;
    while(n)
    {
        n &= n - 1;  //这个知识点还是挺重要的。 n和n-1做与之后，会除去右往左第一个1
        ++ res;
    }
    return res;
}
*/