POJ1386+欧拉回路

#include<cstdio>
#include<vector>
#include<iostream>
#include<cstdlib>
#include<cstring>
using namespace std;
int in[30],out[30],vis[30];
int n;

vector<int> edge[27];

void dfs(int s){
    vis[s]=1;
    for(int i=0;i<edge[s].size();i++)
        if(vis[edge[s][i]]==0)
            dfs(edge[s][i]);
    return ;
}

bool euler(int s){
    int i;
    memset(vis,0,sizeof(vis));
    dfs(s);
    for(i=0;i<26;i++){
        if(vis[i]==0&&edge[i].size()!=0)
            return false;
    }
    return true;
}

int main(){
    int t,n,i,j,len;
    char str[1010];
    scanf("%d",&t);
    while(t--){
        scanf("%d",&n);
        memset(in,0,sizeof(in));
        memset(out,0,sizeof(out));
        for(i=0;i<26;i++)
            edge[i].clear();
        while(n--){
            cin>>str;
            len=strlen(str);
            len--;
            out[str[0]-'a']++;
            in[str[len]-'a']++;
            edge[str[0]-'a'].push_back(str[len]-'a');
            edge[str[len]-'a'].push_back(str[0]-'a');
        }

        //search the eulerian path
        if(euler(str[0]-'a')==false){
            cout<<"The door cannot be opened."<<endl;
            continue;
        }
        int f1=0,f2=0;
        for(i=0;i<26;i++){
            if(in[i]!=out[i]){
                if(in[i]<out[i]){
                    if(out[i]-in[i]==1&&f1==0)
                        f1=1;
                    else
                        break;
                }
                if(out[i]<in[i]){
                    if(in[i]-out[i]==1&&f2==0)
                        f2=1;
                    else
                        break;
                }
            }
        }

        if(i==26)
            cout<<"Ordering is possible."<<endl;
        else
            cout<<"The door cannot be opened."<<endl;
    }
    return 0;
}