[HDU 2553]--N皇后问题(回溯)/N皇后问题的分析

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 using namespace std;
 5 int n, vis[11], cnt, ans[11];
 6 void Search(int cur){
 7     if (cur == n) cnt++;
 8     else for (int i = 0; i < n; i++){
 9         int flag = 1;
10         vis[cur] = i;
11         for (int j = 0; j < cur; j++){
12             if (vis[cur] == vis[j] || cur - vis[cur] == j - vis[j] || cur + vis[cur] == j + vis[j]){
13                 flag = 0;
14                 break;
15             }
16         }
17         if (flag) Search(cur + 1);
18     }
19 }
20 int main(){
21     memset(ans, -1, sizeof(ans));
22     while (~scanf("%d", &n), n){
23         //while (cin >> n, n){
24         cnt = 0;
25         if (ans[n] != -1){
26             printf("%d\n", ans[n]);
27             continue;
28         }
29         Search(0);
30         printf("%d\n", cnt);
31         ans[n] = cnt;
32         //cout << cnt << endl;
33     }
34     return 0;
35 }

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 using namespace std;
 5 int n, vis[11], cnt,T=1, ans[11];
 6 void Show(){
 7     for (int i = 0; i < n; i++){
 8         for (int j = 0; j < n; j++){
 9             if (j) cout << ‘ ‘;
10             if (j == vis[i]) cout << char(3);
11             else
12                 cout << ‘.‘;
13         }
14         cout << endl;
15     }
16 }
17 void Search(int cur){
18     if (cur == n){
19         cout << "Case:" << T++ << endl;
20         Show();
21         cnt++;
22     }
23     else for (int i = 0; i < n; i++){
24         int flag = 1;
25         vis[cur] = i;
26         for (int j = 0; j < cur; j++){
27             if (vis[cur] == vis[j] || cur - vis[cur] == j - vis[j] || cur + vis[cur] == j + vis[j]){
28                 flag = 0;
29                 break;
30             }
31         }
32         if (flag) Search(cur + 1);
33     }
34 }
35 int main(){
36     memset(ans, -1, sizeof(ans));
37     while (cout<<"请输入皇后数：",cin >> n, n){
38         T = 1;
39         cnt = 0;
40         Search(0);
41         cout << "总排列方式："<<cnt << endl;
42     }
43     return 0;
44 }