Debug Challenge

Here is a program with a simple error...can you able to find it?


#include<iostream>
#include<conio.h>
using namespace std;
struct node
{
int key_value;
node* left;
node* right;
};
class btree
{
    public:
        btree();
        ~btree();

        void insert(int key);
        node *search(int key);
        void destroy_tree();

    private:
        void destroy_tree(node *leaf);
        void insert(int key, node *leaf);
        node *search(int key, node *leaf);
       
        node *root;
};
btree::btree()
{
  root=NULL;
}
void btree::destroy_tree(node *leaf)
{
  if(leaf!=NULL)
  {
    destroy_tree(leaf->left);
    destroy_tree(leaf->right);
    delete leaf;
  }
}
void btree::insert(int key, node *leaf)
{
  if(key< leaf->key_value)
  {
    if(leaf->left!=NULL)
     insert(key, leaf->left);
    else
    {
      leaf->left=new node;
      leaf->left->key_value=key;
      leaf->left->left=NULL;    //Sets the left child of the child node to null
      leaf->left->right=NULL;   //Sets the right child of the child node to null
    }
  }
  else if(key>=leaf->key_value)
  {
    if(leaf->right!=NULL)
      insert(key, leaf->right);
    else
    {
      leaf->right=new node;
      leaf->right->key_value=key;
      leaf->right->left=NULL;  //Sets the left child of the child node to null
      leaf->right->right=NULL; //Sets the right child of the child node to null
    }
  }
}

node *btree::search(int key, node *leaf)
{
  if(leaf!=NULL)
  {
    if(key==leaf->key_value)
      return leaf;
    if(key<leaf->key_value)
      return search(key, leaf->left);
    else
      return search(key, leaf->right);
  }
  else return NULL;
}

void btree::insert(int key)
{
  if(root!=NULL)
    insert(key, root);
  else
  {
    root=new node;
    root->key_value=key;
    root->left=NULL;
    root->right=NULL;
  }
}

node *btree::search(int key)
{
  return search(key, root);
}

void btree::destroy_tree()
{
  destroy_tree(root);
}
int main()
{
cout<<"\t\tBST\n\n";
int a,b,in;
while(1)
{

cout<<"Select an operation";
cout<<"1.Insertion";
cout<<"2.Search";
cout<<"3.Destroy";
cout<<"4.Exit";
cin>>a;
switch(a)
{
case 1:
cout<<"Enter a number to insert";
cin>>in;
insert(in);
break;
case 2:
cout<<"Enter a number to search";
cin>>in;
search(in);
break;
case 3:
cout<<"Tree destroyed";
destroy_tree();
break;
case 4:
exit(0);
}
}
getch();
return 0;

}