POJ1386+欧拉回路
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1 #include<cstdio> 2 #include<vector> 3 #include<iostream> 4 #include<cstdlib> 5 #include<cstring> 6 using namespace std; 7 int in[30],out[30],vis[30]; 8 int n; 9 10 vector<int> edge[27]; 11 12 void dfs(int s){ 13 vis[s]=1; 14 for(int i=0;i<edge[s].size();i++) 15 if(vis[edge[s][i]]==0) 16 dfs(edge[s][i]); 17 return ; 18 } 19 20 bool euler(int s){ 21 int i; 22 memset(vis,0,sizeof(vis)); 23 dfs(s); 24 for(i=0;i<26;i++){ 25 if(vis[i]==0&&edge[i].size()!=0) 26 return false; 27 } 28 return true; 29 } 30 31 int main(){ 32 int t,n,i,j,len; 33 char str[1010]; 34 scanf("%d",&t); 35 while(t--){ 36 scanf("%d",&n); 37 memset(in,0,sizeof(in)); 38 memset(out,0,sizeof(out)); 39 for(i=0;i<26;i++) 40 edge[i].clear(); 41 while(n--){ 42 cin>>str; 43 len=strlen(str); 44 len--; 45 out[str[0]-'a']++; 46 in[str[len]-'a']++; 47 edge[str[0]-'a'].push_back(str[len]-'a'); 48 edge[str[len]-'a'].push_back(str[0]-'a'); 49 } 50 51 //search the eulerian path 52 if(euler(str[0]-'a')==false){ 53 cout<<"The door cannot be opened."<<endl; 54 continue; 55 } 56 int f1=0,f2=0; 57 for(i=0;i<26;i++){ 58 if(in[i]!=out[i]){ 59 if(in[i]<out[i]){ 60 if(out[i]-in[i]==1&&f1==0) 61 f1=1; 62 else 63 break; 64 } 65 if(out[i]<in[i]){ 66 if(in[i]-out[i]==1&&f2==0) 67 f2=1; 68 else 69 break; 70 } 71 } 72 } 73 74 if(i==26) 75 cout<<"Ordering is possible."<<endl; 76 else 77 cout<<"The door cannot be opened."<<endl; 78 } 79 return 0; 80 }
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