191. Number of 1 Bits

problem

solution

利用 n&(n-1) 找 n 在二進位表示中有多少個1

class Solution {
public:
    int hammingWeight(uint32_t n) {
        int ret = 0;
        while(n){
            ret++;
            n &=(n-1);
        }
        return ret;
    }
};

analysis

• time complexity O(1)
• space complexity O(1)