【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.

说明：汉明权重就是一个二进制数中为1的数目

最简单的想法，就是除以2求余数，或者就把数字向右移
时间超限：

int hammingWeight(uint32_t n) {    int answer=0;    while(n)    {        if(n%2==1)        {            n++;            n=n/2;        }    }    return answer;}

启发式算法
The analysis can be summarized as: If we first minus a number with 1, and have and operation on the original number and the minus result, the most right of 1 bit becomes 0. We continue these operations until the number becomes 0. We can develop the following code accordingly:

int hammingWeight(uint32_t n) {    int answer=0;    while(n)    {        answer++;        n=n&(n-1);    }    return answer;}