Leetcode-N-Queens II

 1 public class Solution {
 2     public int totalNQueens(int n) {
 3         int res = 0;
 4         int[] place = new int[n];
 5         Arrays.fill(place,-1);
 6         int level = 0;
 7   
 8         while (level!=-1){
 9             if (level>=n){
10                 res++;
11                 level--;
12                 continue;
13             }
14 
15             int val = place[level];
16             val++;
17             while (val<n){
18                 boolean valid = true;
19                 for (int i=0;i<level;i++)
20                     if (val==place[i] || val==place[i]+level-i || val==place[i]-(level-i)){
21                         valid = false;
22                         break;
23                     }
24                 if (valid) break;
25                 else val++;
26             }
27 
28             if (val<n){
29                 place[level]=val;
30                 level++;
31             } else {
32                 place[level]=-1;
33                 level--;
34             }
35         }
36 
37         return res;
38         
39     }
40 }