UVA 10129 Play on Words

#include<bits/stdc++.h>
using namespace std;
int t,l,n,i,ok,root,bin[26],bout[26],fat[26];
int find(int x){
if(fat[x]!=x)return fat[x]=find(fat[x]);
return x;
}
string s;
int main(){
scanf("%d",&t);
while(t--){
scanf("%d",&n);
memset(bin,0,sizeof(bin));
memset(bout,0,sizeof(bout));
for(i=0;i<26;i++)
fat[i]=i;
for(i=1;i<=n;i++){
cin>>s;
int q=s[0]-'a';
int p=s[s.size()-1]-'a';
bin[q]++;
bout[p]++;
int x=find(q);
int y=find(p);
fat[x]=y;
}
l=0;
ok=1;
root=-1;
for(i=0;i<26;i++)
if(bin[i]||bout[i]){
if(abs(bin[i]-bout[i])==1)l++;
else if(bin[i]!=bout[i]){
ok=0;
break;
}
if(root==-1)root=find(i);
if(find(i)!=root){
ok=0;
break;
}
}
if((l==0||l==2)&&ok)puts("Ordering is possible.");
else puts("The door cannot be opened.");
}
return 0;
}