class Solution{
    public:
        int hammingWeight(int n){
            int res= 0;
            /*for(int i = 0;i<32;i++){
                if(n>>i && 1) res ++;
            }*/
            
            //brian-kernighan's algo    
            while(n){
                n = n&(n-1);
                res++

            }
            return res;
        }
};
//n&n-1 resets the last set bit to 0, brian's algo takes o(number of set bits to run) unlike brute force which takes o(total no. of bits). both are o(1).