1 class Solution { 2 public: 3     int totalNQueens(int n) { 4         vector<int> q(n,-1); 5         int result=0; 6         getQueens(0,n,result,q); 7         return result; 8     } 9    10     void getQueens(int level,int &n,int &result,vector<int> &q)11     {12         if(level==n)13         {14             result++;15             return;16         }17         bool flag=false;18         for(int i=0;i<n;i++)19         {20             q[level]=i;21             if(isValid(q,level))22             {23                 getQueens(level+1,n,result,q);24             }25             q[level]=-1;26         }27     }28    29    30     bool isValid(vector<int> &q,int &level)31     {32  33         for(int i=0;i<level;i++)34         {35             if(q[i]==q[level]||abs(q[level]-q[i])==abs(level-i)) return false;36         }37        38         return true;39     }40  41 };