191. Number of 1 Bits (Easy)

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.

题目的意思是，求一个整数的二进制数中有多少个1。

Solutions:

C：
方法一：常规方法，将这个数转化成二进制，在转化过程中计算1的个数

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

方法二：使用&运算

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