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;

}