pku poj 1847 Tram (dfs)

#include < iostream >
using   namespace  std;
int  map[ 101 ][ 101 ];
int  dir[ 101 ];
bool  visit[ 101 ];
int  s,e;
int  n,m,t;
int  best = INT_MAX;
bool  flag;
void  solve( int  t, int  tol)
{    int  i;
    visit[t] = 1 ;
     if (tol > best)
    {   visit[t] = 0 ;
         return  ;
    }
     if (t == e)
    {   visit[t] = 0 ;
         if (tol < best)
            best = tol;
         return  ;
    }
     for (i = 1 ;i <= n;i ++ )
    {   
         if ( ! visit[i] && map[t][i])
        {  
              if (dir[t] == i)
             {   
                 solve(i,tol);
             }
              else
             {   
                 solve(i,tol + 1 );
                 
             }
    
        }
    }
    visit[t] = 0 ;
}
int  main()
{    int  i,j;
    scanf( " %d%d%d " , & n, & s, & e);
     for (i = 1 ;i <= n;i ++ )
    {   
        scanf( " %d " , & m);
         bool index = 0 ;
         while (m -- )
        {    scanf( " %d " , & t);
              if (index == 0 )
             {   dir[i] = t;
                 index = 1 ;
             }
             map[i][t] = 1 ;
        } 
    }
    solve(s, 0 );
     if (best < INT_MAX)
        printf( " %d\n " ,best);
     else
    {   
        printf( " -1\n " );
    }
    system( " pause " );
     return   0 ;
}