uva 10129 play on words——yhx

 1 #include<cstdio>
 2 #include<cstring>
 3 using namespace std;
 4 int in[30],out[30],n;
 5 bool b[30],map[30][30];
 6 void dfs(int p)
 7 {
 8     int i,j,k;
 9     b[p]=1;
10     for (i=0;i<=25;i++)
11       if (map[p][i]&&!b[i])
12         dfs(i); 
13 }
14 bool ok()
15 {
16     int i,j,k,x,y,z;
17     bool b1,b2;
18     b1=b2=0;
19     for (i=0;i<=25;i++)
20       if (in[i]!=out[i])
21       {
22           if (in[i]==out[i]+1) 
23           {
24               if (!b1)
25                 b1=1;
26               else
27                 return 0;
28         }
29           else
30           {
31               if (in[i]==out[i]-1)
32               {
33                   if (!b2)
34                     b2=1;
35                   else
36                     return 0;
37             }
38             else return 0;
39         }
40       }
41     if (b1!=b2) return 0;
42     i=0;
43     while (in[i]==0&&out[i]==0) i++;
44     dfs(i);
45     for (i=0;i<=25;i++)
46       if ((in[i]||out[i])&&!b[i]) return 0;
47     return 1;
48 }
49 int main()
50 {
51     int i,j,k,m,p,q,x,y,z,t;
52     char s[100010];
53     scanf("%d",&t);
54     for (i=1;i<=t;i++)
55     {
56         memset(in,0,sizeof(in));
57         memset(out,0,sizeof(out));
58         memset(b,0,sizeof(b));
59         memset(map,0,sizeof(map));
60         scanf("%d\n",&n);
61         for (j=1;j<=n;j++)
62         {
63             gets(s);
64             map[s[0]-‘a‘][s[strlen(s)-1]-‘a‘]=map[s[strlen(s)-1]-‘a‘][s[0]-‘a‘]=1;
65             in[s[strlen(s)-1]-‘a‘]++;
66             out[s[0]-‘a‘]++;
67         }
68         if (ok()) printf("Ordering is possible.\n");
69         else printf("The door cannot be opened.\n");
70     }
71 }