Binary Search Tree Implementation

///     Raihan Ruhin
///     CSE, Jahangirnagar University.
///     Dhaka-Bangladesh.
///     id: raihanruhin (topcoder / codeforces / codechef / hackerrank / uva / uvalive), 3235 (lightoj)
///     mail: raihanruhin@ (yahoo / gmail / facebook)
///     blog: ruhinraihan.blogspot.com

#include<bits/stdc++.h>
using namespace std;

#define SET(a) memset(a,-1,sizeof(a))
#define CLR(a) memset(a,0,sizeof(a))
#define PI acos(-1.0)

#define MOD 1000000007
#define MX 100010

struct BST{
    int data;
    struct BST *left, *right;
}node;

BST *getNewNode()
{
    BST *tmp;
    tmp=(BST *) malloc(sizeof(BST));
    tmp->left=NULL;
    tmp->right=NULL;
return tmp;
}

void insertNode(BST *root, BST *newNode)
{
    //cout<<root->data<<endl;
    if(newNode->data < root->data)
    {
        if(root->left == NULL) root->left=newNode;
        else insertNode(root->left, newNode);
    }
    else
    {
        if(root->right == NULL) root->right=newNode;
        else insertNode(root->right, newNode);
    }
return;
}

void preOrder(BST *root)
{
    cout<<root->data<<" ";
    if(root->left !=NULL) preOrder(root->left);
    if(root->right !=NULL) preOrder(root->right);
return;
}

void inOrder(BST *root)
{
    if(root->left !=NULL) inOrder(root->left);
    cout<<root->data<<" ";
    if(root->right !=NULL) inOrder(root->right);
return;
}

void postOrder(BST *root)
{
    if(root->left !=NULL) postOrder(root->left);
    if(root->right !=NULL) postOrder(root->right);
    cout<<root->data<<" ";
return;
}

BST *searchBST(BST *root, int key)
{
    while(root!=NULL)
    {
        //cout<<root->data<<endl;
        if(root->data == key) return root;
        else if(key < root->data)
        {
            if(root->left != NULL)
                root=root->left;
            else return NULL;
        }
        else if(key > root->data)
        {
            if(root->right !=NULL)
                root = root->right;
            else return NULL;
        }
    }
return NULL;
}

int main()
{
    BST *root, *newNode;
    root = NULL;
    for(int i=0;i<6;i++)
    {
        newNode = getNewNode();
        cin>>newNode->data;
        if(root==NULL) root=newNode; //BST is not initialized.
        else insertNode(root, newNode);
    }
    preOrder(root);
    cout<<"\n";
    inOrder(root);
    cout<<"\n";
    postOrder(root);
    cout<<"\n";

    int searchElement;
    cin>>searchElement;
    //cout<<searchElement<<endl;
    if(searchBST(root, searchElement)==NULL) cout<<"Not found\n";
    else cout<<"found\n";

return 0;
}
/*
5 4 6 3 7 2
9
*/