Binary Tree - Depth First Search Algorithm

Here is a Binary Tree search algorithm implementation in C for Depth First Search algorithm. The preOrder , inOrder and postOrder implementation are done thru recursive call approach.

	#include <stdio.h>
	#include <stdlib.h>
	struct node {
	struct node *left;
	int data ;
	struct node *right;
	};
	struct node *root = NULL;
	void insertNode(struct node *q, int data)
	{
	if (q == NULL)
	{
	struct node *temp = (struct node *) malloc (sizeof(struct node));
	if (temp == NULL)
	{
	printf("insertNode (%s:%d): malloc failed\n",__FILE__,__LINE__);
	return;
	}
	temp->data = data;
	temp->left = NULL;
	temp->right = NULL;
	root = temp;
	printf("insertNode (%s:%d): First Node\n",__FILE__,__LINE__);
	return;
	}
	else if (q->data == data )
	{
	printf("insertNode (%s:%d): Duplicate entry\n",__FILE__,__LINE__);
	return;
	}
	else if (data < q->data && q->left != NULL )
	{
	q = q->left;
	insertNode(q, data);
	}
	else if (data > q->data && q->right != NULL)
	{
	q = q->right;
	insertNode(q, data);
	}
	else if (data < q->data && q->left == NULL )
	{
	struct node *temp = (struct node *)malloc(sizeof(struct node));
	if (temp == NULL)
	{
	printf("insertNode (%s:%d): malloc failed\n",__FILE__,__LINE__);
	return;
	}
	temp->data = data;
	temp->left = NULL;
	temp->right = NULL;
	q->left = temp;
	return;
	}
	else if (data > q->data && q->right == NULL )
	{
	struct node *temp = (struct node *)malloc(sizeof(struct node));
	if (temp == NULL)
	{
	printf("insertNode (%s:%d): malloc failed\n",__FILE__,__LINE__);
	return;
	}
	temp->data = data;
	temp->left = NULL;
	temp->right = NULL;
	q->right = temp;
	return;
	}
	}
	void inOrderTraversal(struct node *root)
	{
	if(root != NULL)
	{
	inOrderTraversal(root->left);
	printf("%d\n",root->data);
	inOrderTraversal(root->right);
	}
	}
	void preOrderTraversal(struct node *root)
	{
	if(root != NULL)
	{
	printf("%d\n",root->data);
	preOrderTraversal(root->left);
	preOrderTraversal(root->right);
	}
	}
	void postOrderTraversal(struct node *root)
	{
	if(root != NULL)
	{
	postOrderTraversal(root->left);
	postOrderTraversal(root->right);
	printf("%d\n",root->data);
	}
	}
	void main() {
	int n,x;
	int num_nodes = 7;
	for(x=0;x<num_nodes;x++) {
	insertNode(root,x);
	}
	printf("\nInorder Traversal is:\n");
	inOrderTraversal(root);
	printf("\nPreorder Traversal is:\n");
	preOrderTraversal(root);
	printf("\nPostorder Traversal is:\n");
	postOrderTraversal(root);
	}

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