390. Elimination Game

class Solution {public:    int lastRemaining(int n) {        int head=1;        int remain=n;        int setp=1;        bool forward=true;        while(remain>1)        {            if(forward||remain%2==1)            {                head=head+setp;            }            setp*=2;            remain/=2;            forward=!forward;        }        return head;    }};