HDOJ  1181    变形课

题目：​​http://acm.hdu.edu.cn/showproblem.php?pid=1181​​

#include<iostream>
 #include <cstdio>
 #include<cstring>
 using namespace std;
 struct
 {
     char beg;
     char end;
 }M[101];
 bool hash[101],f;
 int N;
 bool DFS(char ch)
 {
      if(ch =='m')
      {
          f= rue;
          return true;
      }
      for(int i = 0;i<N;++i)
          if(M[i].beg==ch&&!hash[i])
          {
             hash[i] = true;
             DFS ( M[i].end );
             hash[i] = false;
          }
      return false;
 }
 int main ()
 {
     string str;
     while (cin >>str)
     {
         N = 0;
         f = false;
         memset ( hash, 0 , sizeof ( hash ) );
         while ( str != "0" )
         {
             M[N].beg = str[0];
             M[N].end = str[ str.size() - 1 ];
             N++;
             cin >> str;
         }
         DFS ( 'b' );
         puts ( f ? "Yes." : "No." );
     }
     return 0;
 }