191. Number of 1 Bits

Write a function that takes an unsigned integer and returns the number of ’1' bits it has (also known as theHamming 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.

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做了个优化，速度提高很多，num+=n&1;

代码：

class Solution {public:    int hammingWeight(uint32_t n) {        int num=0;        int len=0;        while( len++ <32)        {            num += n&1;            n=n>>1;        }        return num;    }};