10106. 「一本通 3.7 例 2」单词游戏

#include<algorithm>
#include<bitset>
#include<complex>
#include<deque>
#include<exception>
#include<fstream>
#include<functional>
#include<iomanip>
#include<ios>
#include<iosfwd>
#include<iostream>
#include<istream>
#include<iterator>
#include<limits>
#include<list>
#include<locale>
#include<map>
#include<memory>
#include<new>
#include<numeric>
#include<ostream>
#include<queue>
#include<set>
#include<sstream>
#include<stack>
#include<stdexcept>
#include<streambuf>
#include<string>
#include<typeinfo>
#include<utility>
#include<valarray>
#include<vector>
#include<cstring>
using namespace std;
#define MAXE 400010
inline int read(){
    char ch=getchar();int res=0,f=1;
    while(ch<'0'ch>'9'){if(ch=='-') f=-1;ch=getchar();}
    while(ch>='0'&&ch<='9') res=res*10+ch-'0',ch=getchar();
    return res*f;
}
int type,n,m;
int in[MAXE],out[MAXE],fa[MAXE];
bool vis[MAXE];
int T;
char as[1010];
int getfa(int x){
    return x==fa[x]?x:fa[x]=getfa(fa[x]);
}
int main(){
    T=read();
    while(T--){
        int Fans=0;
        n=read();m=n;
        memset(in,0,sizeof(in));
        memset(out,0,sizeof(out));
        for(int i=1;i<=26;i++) fa[i]=i;
        for(int i=1;i<=n;i++){
            int x,y;
            cin>>as;
            x=as[0]-'a'+1,y=as[strlen(as)-1]-'a'+1;
            fa[getfa(y)]=getfa(x);
            in[y]++;out[x]++;
        }
        int ans=0;
        for(int i=1;i<=26;i++){
            if(((in[i]!=0out[i]!=0)&&(getfa(i)==i))abs(in[i]-out[i])>1) ans++;//root and son >=2 
        }
        if(ans>=2){puts("The door cannot be opened.");continue;}
        int ans1=0,ans2=0;
        for(int i=1;i<=26;i++) (in[i]>out[i]?ans1++:(in[i]<out[i]?ans2++:ans));
        if(ans1!=ans2ans1>1) puts("The door cannot be opened.");
        else puts("Ordering is possible.");
    }
    return 0;
}