Hdu 1116 Play on Words

#include <iostream>
#include <cstring>
#include <string>
#include <cstdio>
#include <queue>

using namespace std;

const int MAXN = 30;
int in[MAXN]; // 对应入度
int out[MAXN]; //对应出度
int used[MAXN];
bool vis[MAXN];

int Find( int n ){
    if( n!=used[n] )
        used[n] = Find( used[n] );
    return used[n];
}

void Merge( int A, int B ){  // 合并
    int x = Find(A);
    int y = Find(B);
    if( x!=y )
        used[y] = x;
    return ;
}

int main()
{
    int T, N;
    int i,pos;
    int inJudge, outJudge;
    bool bug;
    string temp;
    cin>>T;
    while( T-- ){
        cin>>N;
        for( i=0;i<MAXN;i++ )
            used[i] = i;
        memset( in, 0, sizeof(in) );
        memset( out, 0, sizeof(out) );
        memset( vis, false, sizeof(vis) );  // 初始化
        while( N-- ){
            cin >> temp;
            pos = temp.length() - 1;
            out[ temp[0]-‘a‘ ]++;
            in[ temp[pos]-‘a‘ ]++;
            Merge( temp[0]-‘a‘, temp[pos]-‘a‘ );
            vis[ temp[0]-‘a‘ ] = vis[ temp[pos]-‘a‘ ] =true;
        }
        int counter = 0;  // 用于判断有几个图，如果大于1个，那不能满足题目要求
        for( i=0;i<=‘z‘-‘a‘;i++ )
            if( vis[i] && used[i]==i )
                counter ++;
        if( counter>1 ){
            cout << "The door cannot be opened.\n";
            continue;
        }

        inJudge = outJudge = 0;
        bug = false;
        for( i=0;i<=‘z‘-‘a‘;i++ )
            if( vis[i] ){
                if( in[i]==out[i] )
                    continue;
                else if( in[i]-out[i]==1 )
                    inJudge ++; // 有多少个入度大于出度大1
                else if( out[i]-in[i]==1 )
                    outJudge ++; // 有多少个出度比入度大1
                else
                    bug = true;
            }
        if( bug ){
            cout << "The door cannot be opened.\n";
            continue;
        }
        if( inJudge==1 && outJudge==1 ){
            cout << "Ordering is possible.\n";
            continue;
        }
        if( !inJudge && !outJudge ){
            cout << "Ordering is possible.\n";
            continue;
        }
        cout << "The door cannot be opened.\n";
    }
    return 0;
}