HDU 1116 || POJ 1386 || ZOJ 2016 Play on Words （欧拉回路+并查集）

 1 #include <cstdio>
 2 #include <cstring>
 3 #include <iostream>
 4 
 5 using namespace std ;
 6 
 7 char word[1001] ;
 8 int father[27],out[27],in[27] ,vis[30];
 9 
10 int find_(int x)
11 {
12     if(father[x] != x)
13         father[x] = find_(father[x]) ;
14     return father[x] ;
15 }
16 
17 void mergee(int a,int b)
18 {
19     if(find_(a) != find_(b))
20         father[find_(a)] = find_(b) ;
21 }
22 
23 void Init()
24 {
25     memset(out,0,sizeof(out)) ;
26     memset(in,0,sizeof(in)) ;
27     for(int i = 0 ; i < 26 ; i++)
28         father[i] = i ;
29     memset(vis,0,sizeof(vis)) ;
30 }
31 
32 int main()
33 {
34     int T ;
35     cin >> T ;
36     int n ;
37     while(T--)
38     {
39         cin >> n ;
40         Init() ;
41         while(n -- )
42         {
43             scanf("%s",word) ;
44             int u = word[0]-‘a‘ ;
45             int v = word[strlen(word)-1]-‘a‘ ;
46             mergee(u,v) ;
47             out[u] ++ ;
48             in[v] ++ ;
49             vis[u] = vis[v] = 1 ;
50         }
51         int cnt = 0,cnt1 = 0 ,cnt2 = 0 ;
52         for(int i = 0 ; i < 26 ; i++)
53         {
54             if(vis[i] && father[i] == i)
55             {
56                 cnt ++ ;
57             }
58         }
59         if(cnt > 1)
60         {
61             puts("The door cannot be opened.") ;
62             continue ;
63         }
64         bool flag = true ;
65         for(int i = 0 ; i < 26 ; i++)
66         {
67             if(vis[i] && out[i] != in[i])
68             {
69                 if(out[i]-in[i] == 1)
70                 {
71                     cnt1 ++ ;
72                     if(cnt1 > 1)
73                     {
74                         flag = false ;
75                         break ;
76                     }
77                 }
78                 else if(in[i]-out[i] == 1)
79                 {
80                     cnt2 ++ ;
81                     if(cnt2 > 1)
82                     {
83                         flag = false ;
84                         break ;
85                     }
86                 }
87                 else
88                 {
89                     flag = false ;
90                     break ;
91                 }
92             }
93         }
94         if(!flag) puts("The door cannot be opened.") ;
95         else puts("Ordering is possible.") ;
96     }
97     return 0 ;
98 }