191. Number of 1 Bits

题目

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.

Credits:

Special thanks to @ts for adding this problem and creating all test cases.

Subscribe to see which companies asked this question.

思路

n&(n-1)会把n最后的一个bit为1的改成0，循环遍历计算bit 1的个数

代码

class Solution {
public:
int hammingWeight(uint32_t n) {
int sum = 0;

while(n)
{
sum++;
n &= (n-1);
}

return sum;
}
};