C++11(clang++ 3.9) 解法, 执行用时: 74ms, 内存消耗: 476K, 提交时间: 2019-07-26 23:17:39

#include<algorithm>
#include<iostream>
#include<cstring>
#include<cstdio>
#include<cmath>
#include<queue>
using namespace std;
char s[1001];
int t,n,m,a,b,c;
int fa[50],u[50],v[50];
int find(int x){
	return fa[x]==x?x:fa[x]=find(fa[x]);
}
int main(){
	scanf("%d",&t);
	while(t--){
		memset(u,0,sizeof u);
		memset(v,0,sizeof v);
		scanf("%d",&n);
		a=b=c=0;
		for(int i=1;i<=30;i++){
			fa[i]=i;
		}
		for(int i=1;i<=n;i++){
			scanf("%s",s+1);
			m=strlen(s+1);
			int l=s[1]-'a'+1,r=s[m]-'a'+1;
			fa[find(l)]=find(r);
			u[l]++;
			v[r]++;
		}
		for(int i=1;i<=26;i++){
			if(((u[i]||v[i])&&(find(i)==i))||u[i]-v[i]>1||u[i]-v[i]<-1){
				a++;
			}
		}
		if(a>1){
			puts("The door cannot be opened.");
			continue;
		}
		for(int i=1;i<=26;i++){
			if(u[i]>v[i]){
				b++;
			}
			else if(u[i]<v[i]){
				c++;
			}
		}
		if(b!=c||b>1){
			puts("The door cannot be opened.");
			continue;
		}
		puts("Ordering is possible.");
	}
	return 0;
}