n皇后问题

 1 //u为行，i为列
 2 
 3 #include<iostream>
 4 #include<cstdio>
 5 using namespace std;
 6 const int N=20;
 7 char g[N][N];
 8 bool col[N],dg[N],udg[N];
 9 int n;
10 void dfs(int u){
11     if(u==n)
12     {
13         for (int i = 0; i <n ; ++i) puts(g[i]);
14         puts("");
15         return;
16     }
17     for (int i = 0; i <n ; ++i) {
18         if( !col[i] && !dg[u+i] && !udg[n-u+i] ){
19             g[u][i]=‘Q‘;
20             col[i]=dg[u+i]=udg[n-u+i]=true;
21 
22             dfs(u+1);
23 
24             col[i]=dg[u+i]=udg[n-u+i]=false;
25             g[u][i]=‘.‘;
26         }
27     }
28 }
29 int main(){
30     scanf("%d",&n);
31     for (int i = 0; i <n ; ++i)
32         for (int j = 0; j <n ; ++j)
33             g[i][j]=‘.‘;
34 
35     dfs(0);
36 
37     return 0;
38 }