leetcode 191. 位1的个数（java & python3）

java：

public class Solution {
    // you need to treat n as an unsigned value
    public int hammingWeight(int n) {
        int res = 0;
        for(int i = 0; i < 32; i++){
            if((n & (1 << i)) != 0){
                res ++;
            }
        }
        return res;
    }
}

public class Solution {
    // you need to treat n as an unsigned value
    public int hammingWeight(int n) {
        int res = 0;
        while(n != 0){
            res ++;
            n &= n-1;
        }
        return res;
    }
}

python3;

利用 n&（n-1）

class Solution:
    def hammingWeight(self, n: int) -> int:
        res = 0
        while n:
            res += 1
            n &= n - 1
        return res

逐位判断

class Solution:
    def hammingWeight(self, n: int) -> int:
        res = 0
        while n:
            res += n & 1
            n >>= 1
        return res