191_numberOf1Bits.md

[Python] n & (n-1) trick + even faster, explained 🌟

Using __builtin_popcount

class Solution {
public:
    int hammingWeight(uint32_t n) {
        return (__builtin_popcount(n));
    }
};

Using n=n&(n-1) trick

• Each time of "n &= n - 1", we delete one '1' from n.

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

READ:

• [Python] n & (n-1) trick + even faster, explained
• Short code of C++, O(m) by time, m is the count of 1's, and another several method of O(1) time