1 public class Solution { 2     int result;   3     int[] A;  4     public int totalNQueens(int n) { 5         A = new int[n];   6         nqueens(0, n);   7         return result;     8     } 9 10      public void nqueens(int cur, int n){  11          if(cur==n) result++;  12          else {  13              for(int i=0;i<n;i++){  14                  A[cur] = i;  15                  if(valid(cur)){  16                      nqueens(cur+1, n);  17                  }  18              }  19          }  20      }  21      public boolean valid(int r){  22          for(int i=0;i<r;i++){  23              if(A[i]==A[r]|| Math.abs(A[i]-A[r])==r-i){  24                  return false;  25              }  26          }  27          return true;  28      }  29 }