leetcode: Permutations I II

vector<vector<int> > res;        sort(num.begin(), num.end());        res.push_back(num);        if(num.size() < 2){            return res;        }        while(true){                  int i = num.size() - 1;            while(true){                int ii = i;                --i;                if(num[i] < num[ii]){                    int j = num.size();                    while(num[i] >= num[--j]);                    swap(num[i], num[j]);                    reverse(num.begin() + ii, num.end());                    res.push_back(num);                    break;                }                if(i == 0){                    return res;                }            }        }