درخت پیشوندی

#include<iostream>
#include<string>
#define alph 26
using namespace std;
/*	node structure (of course it has 26 children) and add and search
 functions are for lower case alphabets	*/

struct node
{
bool value;	//if it's end of word or not
node* next[alph];	//all alphabet for next digits
node()	//initialization, the constructor
{
this->value= 0;
for(int i=0; i<alph ; i++)
next[i]= NULL;	//there is no next digit initialy
}
};

void add( node* head , string word );
bool search( node* head , string query );

int main()
{
node* root= new node();
int n;
cout <<" enter number of words you wanna insert " <<endl;
cin>> n;
for(int i=0; i<n; i++)
{
cout <<"enter word "<<endl;
string word;
cin>>word;
add(root,word);
}
cout <<" enter number of words you wanna search " <<endl;
cin>> n;
for(int i=0; i<n; i++)
{
cout <<"enter query "<<endl;
string word;
cin>>word;
if(search(root,word))
cout<<"YES"<<endl;
else
cout<<"NO"<<endl;
}
return 0;
}
void add( node* head , string word )
{
if(word.length()==1)
{
if(head->next[word[0]-'a']==NULL)
head->next[word[0]-'a']= new node();
//%22word-%27a%27%22 makes an index alphabet number, 26 more or less of course
head->next[word[0]-'a']->value = 1;
return;
}
else //if(word.length()>1)
{
if(head->next[word[0]-'a']==NULL)
head->next[word[0]-'a']= new node();
return add(head->next[word[0]-'a'], word.substr(1,word.length()-1));
}
}
bool search(node*head,string query)
{
if(query.length()==1)
{
if(head->next[query[0]-'a']==NULL)
return false;
else if	(head->next[query[0]-'a']->value)
return true;
else return false;
}
else
{
if(head->next[query[0]-'a']==NULL)
return false;
else return search(head->next[query[0]-'a'],query.substr(1,query.length()-1));
}
}