191 Number of 1 Bits

Posted 2020-10-01

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.

bit manipulation 操作很弱啊, 要把整数看作二进制数, 进行与、或、异或的运算

public int hammingWeight(int n) {
        if (n == 1) {
            return 1;
        }
        int res = 0;
        for (int i = 0; i < 32; ++i) {
            res += (n & 1);
            n = n >> 1;
        }
        return res;

    }