poj1386欧拉回路的判定

#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <stack>
#include <queue>
#include <vector>
#include <map>
#include <string>
#include <iostream>
using namespace std;
int father[1000];
int getfather(int x)
{
    if(x!=father[x]) father[x]=getfather(father[x]);
    return father[x];
}

void add(int a,int b)
{
    int fa=getfather(a);int fb=getfather(b);
    if(fa!=fb) father[fa]=fb;
}
int vis[111111];
int out[100],in[1000];
bool ok()
{
    int one=0;int two=0;
    int sum=0;
    for(int i=0;i<26;i++)
        if(vis[i]) if(father[i]==i) sum++;
    if(sum>1) return false;
    for(int i=0;i<26;i++){
        if(in[i]-out[i]==1) one++;
        if(out[i]-in[i]==1) two++;
        if(out[i]==in[i]) continue;
        if(out[i]-in[i]>1||in[i]-out[i]>1) return false;
    }
    return ((one==1&&two==1)||(one==0&&two==0));//  return one <= 1 && two <= 1
}
int main()
{
    int Icase;int n;
    int G[100][100];
    char str[2000];
    cin>>Icase;
    while(Icase--){
        for(int i=0;i<26;i++) father[i]=i;
        cin>>n;int ans=0;
        memset(in,0,sizeof(in));
        memset(out,0,sizeof(out));
        memset(G,0,sizeof(G));
        memset(vis,0,sizeof(vis));
        for(int i=0;i<n;i++){
            scanf("%s",str);int a=str[0]-'a';int len=strlen(str);int b=str[len-1]-'a';
            add(a,b);in[b]++;out[a]++;vis[a]=1;vis[b]=1;
        }
        if(ok()) cout<<"Ordering is possible."<<endl;
        else cout<<"The door cannot be opened."<<endl;

    }
    return 0;
}