[题解]UVA10129 Play on Words

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 using namespace std;
 5 #define Max 30
 6 #define MaxLen 1010
 7 int T,n,Bgn;
 8 int Edge[Max][Max],Chu[Max],Ru[Max];
 9 bool vis[Max];
10 char str[MaxLen];
11 inline void Get_int(int &Ret)
12 {
13     char ch;
14     bool flag=false;
15     for(;ch=getchar(),ch<‘0‘||ch>‘9‘;)
16         if(ch==‘-‘)
17             flag=true;
18     for(Ret=ch-‘0‘;ch=getchar(),ch>=‘0‘&&ch<=‘9‘;Ret=Ret*10+ch-‘0‘);
19     flag&&(Ret=-Ret);
20 }
21 inline void Read()
22 {
23     Get_int(n);
24     memset(vis,false,sizeof(vis));
25     memset(Chu,0,sizeof(Chu));
26     memset(Ru,0,sizeof(Ru));
27     memset(Edge,0,sizeof(Edge));
28     int i,u,v,Len;
29     for(i=1;i<=n;i++)
30     {
31         do
32         {
33             scanf("%s",str);
34             Len=strlen(str);
35         }while(!Len);
36         u=str[0]-‘a‘+1; v=str[Len-1]-‘a‘+1;
37         //if(u==v) continue;
38         Edge[u][v]++;Edge[v][u]++;
39         Chu[u]++;Ru[v]++;
40         vis[u]=vis[v]=true;
41     }
42     Bgn=u;
43 }
44 void Dfs(int u)
45 {
46     vis[u]=false;
47     for(int i=1;i<=26;i++)
48         if(Edge[u][i]&&vis[i])
49             Dfs(i);
50 }
51 inline bool Solve()
52 {
53     int i,ch=0,ru=0;
54     Dfs(Bgn);
55     for(i=1;i<=26;i++)
56     {
57         if(vis[i])
58             return false;
59         if(Chu[i]!=Ru[i])
60         {
61             if(Chu[i]-Ru[i]==1)
62                 ch++;
63             else if(Ru[i]-Chu[i]==1)
64                 ru++;
65             else
66                 return false;
67         }
68     }
69     if((ch==1&&ru==1)||(ch==0&&ru==0))
70         return true;
71     return false;
72 }
73 int main()
74 {
75     Get_int(T);
76     while(T--)
77     {
78         Read();
79         if(Solve())
80             printf("Ordering is possible.\n");
81         else
82             printf("The door cannot be opened.\n");
83     }
84     return 0;
85 }