USACO 2.3.1 Longest Prefix --- Trie

/*
 PROG:   prefix
 ID  :   
 LANG:   C++
 */
 #include <string.h>
 #include <cstdio>
 #include <cstdlib>
 #include <cstring>
 #include <iostream>
 #include <memory.h>
 #include <algorithm>
 using namespace std;
 
 struct Trie_Node
 {
     bool IsEnd;
     Trie_Node *branch[26];
     Trie_Node(): IsEnd( false )
     {
         memset( branch, 0, sizeof(branch) );
     }// Init
 };
 
 class Trie
 {    
     public:
         Trie();
         void Trie_Insert( char tt[] );
         void Trie_Find( long j );
     
     private:
         Trie_Node *root;
 }t; // type class "Trie" object t
 
 long slen;
 bool prefix[200400];
 char line[204], ss[200400];
 
 Trie::Trie()
 {
     root = new Trie_Node();
 }// Trie
 
 void Trie::Trie_Insert( char tt[] )
 {
     Trie_Node *ptr = root;
     int tlen = strlen( tt );
     for ( int i=0; i<tlen; ++i )
     {
         if ( ptr->branch[ tt[i]-'A' ]==NULL )
         {
             Trie_Node *tmp = new Trie_Node();
             ptr->branch[ tt[i]-'A' ] = tmp;
         }
                         
         ptr = ptr->branch[ tt[i]-'A' ];
     }
                     
     ptr->IsEnd = true;
 }// Trie_Insert
 
 void ReadData()
 {    
     while ( gets( line ) )
     {
         if ( line[0]=='.' ) break;
         
         char *tok = strtok( line, " " );
         while ( tok )
         {
             t.Trie_Insert( tok );
             //printf("%s\n", tok);
             tok = strtok( NULL, " " );
         }// Insert
     }
     
     char str[204];
     while ( gets( str ) )
     {
         strcat( ss, str );
     }
     
     slen = strlen( ss );
     
     return ;
 }// ReadData
 
 void Trie::Trie_Find( long j )
 {
     Trie_Node *ptr = root;
     for ( ; ; ++j )
     {
         ptr = ptr->branch[ ss[j]-'A' ];
         if ( ss[j]=='\0' || ptr==NULL )
             return ;
         if ( ptr->IsEnd )
             prefix[ j+1 ]=true;
     }
     
     return ;
 }// Trie_Find
 
 void Solve()
 {
     prefix[0] = true;
     for ( long i=0; i<slen; ++i )
     {
         if ( !prefix[i] )   continue;
         
         t.Trie_Find( i );
     }// Searching
     
     int result;
     for ( result=slen; !prefix[result]; --result );
     printf("%d\n", result);
 
     return ;
 }// Solve
 
 int main()
 {
     freopen("prefix.in", "r", stdin);
     freopen("prefix.out", "w", stdout);
 
     ReadData();
     Solve();
     
 //    system("pause");
     return 0;
 }