hdu 1116 Play on Words

http://acm.hdu.edu.cn/showproblem.php?pid=1116

#include<iostream>
#include<string>
using namespace std;
int in[30],out[30],bin[30],d[30];
int findx(int x)
{
 if(bin[x]==-1) bin[x]=x;
 while(x!=bin[x]) x=bin[x];
 return x;
}

int main()
{
 int t,n,i,x,y;
 string str;
 cin>>t;
 while(t--)
 {
  cin>>n;
  memset(bin,-1,sizeof(bin)); memset(d,0,sizeof(d));
  memset(in,0,sizeof(in)),memset(out,0,sizeof(out));
  for(i=1;i<=n;i++)
  {
   cin>>str;
   x=str[0]-'a'+1; d[x]=1;
   y=str[str.size()-1]-'a'+1; d[y]=1;
   in[y]++,out[x]++;
            x=findx(x);
   y=findx(y);
   if(x!=y) bin[y]=x;
  }
  int cnt=0;
  for(i=1;i<=26;i++)
   if(d[i]&&bin[i]==i) cnt++;
  if(cnt>1)
  {
   cout<<"The door cannot be opened."<<endl; continue;
  }
      
  for(cnt=0,i=1;i<=26;i++)
   if(in[i]!=out[i]) d[cnt++]=i;
  if(cnt==0)  { cout<<"Ordering is possible."<<endl; continue;}
  if(cnt==2)
   if((in[d[0]]==out[d[0]]+1&&in[d[1]]==out[d[1]]-1)||(in[d[0]]==out[d[0]]-1&&in[d[1]]==out[d[1]]+1))
   {
    cout<<"Ordering is possible."<<endl; continue;
   }
    cout<<"The door cannot be opened."<<endl;
 }
 return 0;
}