1 class Solution { 2 public: 3     void nextPermutation(vector
     
       &num) { 4         // Note: The Solution object is instantiated only once and is reused by each test case. 5         int n = num.size(); 6         if (n <= 1) 7             return; 8         int i; 9         for (i = n - 2; i >= 0; i--){10             if (num[i]
      
       num[i] && num[j]