ZOJ - 1008 Gnome Tetravex

 1 #include<stdio.h>
 2 #include<string.h>
 3 const int maxn=25+5;
 4 int num[maxn],curnum,vis[maxn],ok;
 5 struct node{
 6     int top,bot,right,left;
 7     bool operator==(const node &t)
 8     {
 9         return top==t.top && bot==t.bot && right==t.right && left==t.left;
10     }
11 }square[maxn],curque[maxn];
12 void dfs(int cur,int n);
13 int main()
14 {
15     int n,T=0,blank=0;
16     while(scanf("%d",&n)==1 && n){
17         memset(num,0,sizeof(num));
18         memset(vis,0,sizeof(vis));
19         curnum=0;
20         T++;
21         ok=0;
22         for(int i=0;i<n*n;i++){
23             int flag=1;
24             scanf("%d%d%d%d",&square[i].top,&square[i].right,&square[i].bot,&square[i].left);
25             for(int j=0;j<curnum;j++){
26                 if(square[i]==curque[j]){
27                     num[j]++;
28                     flag=0;
29                     break;
30                 }
31             }
32             if(flag){
33                 num[curnum]++;
34                 curque[curnum++]=square[i];
35             }
36         }
37         dfs(0,n);
38         if(blank)
39             printf("\n");
40         else
41             blank=1;
42         if(ok)
43             printf("Game %d: Possible\n",T);
44         else
45             printf("Game %d: Impossible\n",T);
46 
47     }
48     return 0;
49 }
50 void dfs(int cur,int n)
51 {
52     int xpos=cur%n;
53     int ypos=cur/n;
54     if(ok || cur==n*n){
55         ok=1;
56         return;
57     }
58     for(int i=0;i<curnum;i++){
59         if(num[i]){
60             if(xpos>0)
61                 if(square[cur-1].right!=curque[i].left)
62                 continue;
63             if(ypos>0)
64                 if(square[cur-n].bot!=curque[i].top)
65                 continue;
66             num[i]--;
67             square[cur]=curque[i];
68             dfs(cur+1,n);
69             num[i]++;
70         }
71     }
72 }