USACO 2.3.1 Longest Prefix --- Trie

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  1 /*

  2 PROG:   prefix

  3 ID  :   ouyangyewei

  4 LANG:   C++

  5 */

  6 #include <string.h>

  7 #include <cstdio>

  8 #include <cstdlib>

  9 #include <cstring>

 10 #include <iostream>

 11 #include <memory.h>

 12 #include <algorithm>

 13 using namespace std;

 14 

 15 struct Trie_Node

 16 {

 17     bool IsEnd;

 18     Trie_Node *branch[26];

 19     Trie_Node(): IsEnd( false )

 20     {

 21         memset( branch, 0, sizeof(branch) );

 22     }// Init

 23 };

 24 

 25 class Trie

 26 {    

 27     public:

 28         Trie();

 29         void Trie_Insert( char tt[] );

 30         void Trie_Find( long j );

 31     

 32     private:

 33         Trie_Node *root;

 34 }t; // type class "Trie" object t

 35 

 36 long slen;

 37 bool prefix[200400];

 38 char line[204], ss[200400];

 39 

 40 Trie::Trie()

 41 {

 42     root = new Trie_Node();

 43 }// Trie

 44 

 45 void Trie::Trie_Insert( char tt[] )

 46 {

 47     Trie_Node *ptr = root;

 48     int tlen = strlen( tt );

 49     for ( int i=0; i<tlen; ++i )

 50     {

 51         if ( ptr->branch[ tt[i]-'A' ]==NULL )

 52         {

 53             Trie_Node *tmp = new Trie_Node();

 54             ptr->branch[ tt[i]-'A' ] = tmp;

 55         }

 56                         

 57         ptr = ptr->branch[ tt[i]-'A' ];

 58     }

 59                     

 60     ptr->IsEnd = true;

 61 }// Trie_Insert

 62 

 63 void ReadData()

 64 {    

 65     while ( gets( line ) )

 66     {

 67         if ( line[0]=='.' ) break;

 68         

 69         char *tok = strtok( line, " " );

 70         while ( tok )

 71         {

 72             t.Trie_Insert( tok );

 73             //printf("%s\n", tok);

 74             tok = strtok( NULL, " " );

 75         }// Insert

 76     }

 77     

 78     char str[204];

 79     while ( gets( str ) )

 80     {

 81         strcat( ss, str );

 82     }

 83     

 84     slen = strlen( ss );

 85     

 86     return ;

 87 }// ReadData

 88 

 89 void Trie::Trie_Find( long j )

 90 {

 91     Trie_Node *ptr = root;

 92     for ( ; ; ++j )

 93     {

 94         ptr = ptr->branch[ ss[j]-'A' ];

 95         if ( ss[j]=='\0' || ptr==NULL )

 96             return ;

 97         if ( ptr->IsEnd )

 98             prefix[ j+1 ]=true;

 99     }

100     

101     return ;

102 }// Trie_Find

103 

104 void Solve()

105 {

106     prefix[0] = true;

107     for ( long i=0; i<slen; ++i )

108     {

109         if ( !prefix[i] )   continue;

110         

111         t.Trie_Find( i );

112     }// Searching

113     

114     int result;

115     for ( result=slen; !prefix[result]; --result );

116     printf("%d\n", result);

117 

118     return ;

119 }// Solve

120 

121 int main()

122 {

123     freopen("prefix.in", "r", stdin);

124     freopen("prefix.out", "w", stdout);

125 

126     ReadData();

127     Solve();

128     

129 //    system("pause");

130     return 0;

131 }