Binary search tree

# include <iostream>
# include <string>
# include <cstring>
# include <string.h>
# include <windows.h>

using namespace std;

struct node
{
	int value;
	node *left;
	node *right;
};

node *root = NULL;

void insert_tree(int key,node *root)
{
	if (::root == NULL)
	{
		::root = new node;
		::root->value = key;
		::root->left = NULL;
		::root->right = NULL;
	}
	else
	{
		if (key < root->value)
		{
			if (root->left == NULL)
			{
				//insert 
				root->left = new node;
				root->left->value = key;
				root->left->left = NULL;
				root->left->right = NULL;
			}
			else
			{
				insert_tree(key, root->left);
			}
		}
		else if (key > root->value)
		{
			if (root->right == NULL)
			{
				//insert
				root->right = new node;
				root->right->value = key;
				root->right->left = NULL;
				root->right->right = NULL;
			}
			else
			{
				insert_tree(key,root->right);
			}
		}
		else
		{
			cout << "you entered this value before so i will ignore it" << endl;
			return;
		}
	}
}

node* search(int key, node *root)
{
	if (root != NULL)
	{
		if (key == root->value)
			return root;
		if (key<root->value)
			search(key, root->left);
		else
		    search(key, root->right);

	}
	else 
	{
		cout << "Can't Find the Value you searched" << endl;
		exit(0);
	}
}

int main()
{
	insert_tree(10,root);
	insert_tree(6, root);
	insert_tree(14, root);
	insert_tree(5, root);
	insert_tree(8, root);
	insert_tree(11, root);
	insert_tree(18, root);

	node *found = search(1, root);
	cout << found->value <<" was Found" << endl;

	return 0; 
}