Play on Words 欧拉通路（回路）判断

　　　　　　　　　　　　　　　　　　　　　　Play on Words
note: 判断一下连通性。
  1 #include <iostream>
  2 #include <cstdio>
  3 #include <cstring>
  4 #include <cmath>
  5 #include <algorithm>
  6 #include <string>
  7 #include <vector>
  8 #include <set>
  9 #include <map>
 10 #include <stack>
 11 #include <queue>
 12 #include <sstream>
 13 #include <iomanip>
 14 using namespace std;
 15 typedef long long LL;
 16 const int INF=0x4fffffff;
 17 const int EXP=1e-5;
 18 const int MS=100005;
 19 const int SIZE=26;
 20 
 21 int n;
 22 char word[MS];
 23 int od[SIZE],id[SIZE];
 24 
 25 int appear[SIZE];
 26 int fa[SIZE];
 27 
 28 struct edge
 29 {
 30       int u,v;
 31 }edges[MS];
 32 
 33 void fa_init()
 34 {
 35       for(int i=0;i<SIZE;i++)
 36             fa[i]=-1;
 37 }
 38 
 39 int find(int x)
 40 {
 41       int s;
 42       for(s=x;fa[s]>=0;s=fa[s]);
 43 
 44       while(s!=x)
 45       {
 46             int tmp=fa[x];
 47             fa[x]=s;
 48             x=tmp;
 49       }
 50       return s;
 51 }
 52 
 53 void merge(int x,int y)
 54 {
 55       int f1=find(x);
 56       int f2=find(y);
 57       int tmp=fa[f1]+fa[f2];
 58       if(fa[f1]>fa[f2])
 59       {
 60             fa[f1]=f2;
 61             fa[f2]=tmp;
 62       }
 63       else
 64       {
 65             fa[f2]=f1;
 66             fa[f1]=tmp;
 67       }
 68 }
 69 
 70 bool connect()
 71 {
 72       int u,v,i;
 73       fa_init();
 74       for(i=0;i<n;i++)
 75       {
 76             u=edges[i].u;
 77             v=edges[i].v;
 78             if(u!=v&&find(u)!=find(v))
 79                   merge(u,v);
 80       }
 81 
 82       int first=-1;
 83       for( i=0;i<SIZE;i++)
 84       {
 85             if(appear[i]==0)
 86                   continue;
 87             if(first==-1)
 88                   first=i;
 89             else if(find(i)!=find(first))
 90                   break;
 91       }
 92       if(i<SIZE)
 93             return false;
 94       return true;
 95 }
 96 
 97 int main()
 98 {
 99       int u,v;
100       int i,j;
101       int T;
102       scanf("%d",&T);
103       while(T--)
104       {
105             memset(od,0,sizeof(od));
106             memset(id,0,sizeof(id));
107             memset(appear,0,sizeof(appear));
108             scanf("%d",&n);
109             for(i=0;i<n;i++)
110             {
111                   scanf("%s",word);
112                   u=word[0]-'a';
113                   v=word[strlen(word)-1]-'a';
114                   od[u]++;
115                   id[v]++;
116 
117                   appear[u]=appear[v]=1;
118                   edges[i].u=u;
119                   edges[i].v=v;
120             }
121 
122             bool Euler=true;
123             int one=0,none=0;
124             for(i=0;i<SIZE;i++)
125             {
126                   if(appear[i]==0)
127                         continue;
128                   if(od[i]-id[i]>=2||id[i]-od[i]>=2)
129                   {
130                         Euler=false;
131                         break;
132                   }
133                   if(od[i]-id[i]==1)
134                   {
135                         one++;
136                         if(one>1)
137                         {
138                               Euler=false;
139                               break;
140                         }
141                   }
142                   if(id[i]-od[i]==1)
143                   {
144                         none++;
145                         if(none>1)
146                         {
147                               Euler=false;
148                               break;
149                         }
150                   }
151             }
152             if(one!=none)
153                   Euler=false;
154             if(connect()==false)
155                   Euler=false;
156             if(Euler)
157                   printf("Ordering is possible.
");
158             else
159                   printf("The door cannot be opened.
");
160       }
161       return 0;
162 }