N皇后问题（dfs）

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 using namespace std;
 5 bool a[11], b[22], c[22], vis[11][11];
 6 int d[11];
 7 int ans = 0, n;
 8 void dfs(int x){
 9     if(x == n){
10         ans ++;
11         return;
12     }
13     for(int i = 0; i < n; i ++){
14         if(a[i] || b[x+i] || c[x-i+n])continue;
15         a[i] = b[x+i] = c[x-i+n] = vis[x][i] = true;
16         dfs(x+1);
17         a[i] = b[x+i] = c[x-i+n] = vis[x][i] = false;
18     }
19 }
20 int main(){
21     for(int i = 1; i < 11; i ++){
22         memset(a,false,sizeof(a));
23         memset(b,false,sizeof(b));
24         memset(c,false,sizeof(c));
25         memset(vis,false,sizeof(vis));
26         ans = 0;
27         n = i;
28         dfs(0);
29         d[i] = ans;
30     }
31     while(~scanf("%d",&n)&&n){
32         cout << d[n] << endl;
33     }
34 }