next permutation

class Solution {public:void nextPermutation(vector<int> &num) {int n = num.size();if (n == 1)return;for (int i = n - 2, ii = n - 1; i >= 0; i--, ii--)if (num[i] < num[ii]){int j = n - 1;while (num[j] <= num[i])j--;//从尾部找到第一个比num[i]大的数，一定可以找到swap(num[i], num[j]);reverse(num.begin() + ii, num.end());return;}reverse(num.begin(), num.end());}};