TLE：csu 1205 放石子游戏

表示第一次用dfs。。。

 1 # include <stdio.h>
 2 # include <string.h>
 3 
 4 char board[1001][1001];
 5 char vis[1001];
 6 int trace[1001];
 7 int N, M, ans;
 8 
 9 void dfs(int x, int y);
10 void special_dfs(int x, int y, int trace[]);
11 
12 int main()
13 {
14     int i, j, x, y;
15     
16     while (~scanf("%d%d", &N, &M))
17     {
18         ans = 0;
19         for (i = 0; i < M; ++i)
20         {
21             scanf("%d%d", &x, &y);
22             board[x][y] = 1;
23         }       
24         for (i = 1; i <= N; ++i)
25             if (!vis[i] && board[1][i]) dfs(1, i);
26         if (ans == 1) 
27         {
28             printf("So easy\n");
29             for (i = 1; i <= N; ++i)
30                 if (!vis[i] && board[1][i]) special_dfs(1, i, trace);
31         }
32         else if (ans == 0) printf("You trick me\n");
33         else printf("Ask God for help\n");        
34         memset(board, 0, sizeof(board));    
35         memset(vis, 0, sizeof(vis));
36         memset(trace, 0, sizeof(trace));
37     }
38     
39     return 0;
40 }
41 
42 void dfs(int x, int y)
43 {
44     int i;
45     if (x == N) {++ans; return;}
46     vis[y] = 1;
47     for (i = 1; i <= N; ++i)
48         if (!vis[i] && board[x+1][i]) 
49             dfs(x+1, i);
50     vis[y] = 0;
51 }
52 void special_dfs(int x, int y, int trace[])
53 {
54     int i;
55     if (x == N) 
56     { 
57         trace[x] = y;
58         printf("%d", trace[1]);
59         for (i = 2; i <= N; ++i)
60             printf(" %d", trace[i]);
61         printf("\n");
62         return;
63     }
64     vis[y] = 1;
65     trace[x] = y;
66     for (i = 1; i <= N; ++i)
67         if (!vis[i] && board[x+1][i]) 
68             special_dfs(x+1, i, trace);
69     vis[y] = 0;
70 }

结果应该没错。。