[LeetCode]Number of 1 Bits

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.

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

有个简单的规律， Wegner (1960)发现的。利用x和x-1之间的关系。

 1 class Solution {
 2 public:
 3     int hammingWeight(uint32_t n) {
 4         int result = 0;
 5         while(n)
 6         {
 7             n=n&(n-1);
 8             result++;
 9         }
10         return result;
11     }
12 };