Boundary traversal of binary tree

#include <iostream>

struct Node
{
	int data;
	struct Node *left, *right;
	Node(int i){ data = i; left = right = 0; }
};

void print(Node * root){
	std::cout << root->data <<" ";
}

void traverse_R(Node* root, int a){
	if (root->left != 0 && root->right!=0)
		traverse_R(root->left, 0);
	if (root->right == 0 && root->left == 0 && a == 0) print(root);

	if (root->right != 0)
		traverse_R(root->right, a);
	else if (root->left != 0)
		traverse_R(root->left, a);
	if (a) print(root);
}


void traverse_L( Node * root, int a){
	if(a) print(root);

	if (root->left != 0)
		traverse_L(root->left,a);
	else if (root->right != 0)
		return traverse_L(root->right,a);
	
	if (root->right != 0)
		traverse_L(root->right, 0);
	if (root->right == 0 && root->left == 0 && a == 0) print(root);

}

void traverse(Node* root){
	if (root){
		print(root);
		if (root->left) traverse_L(root->left,1);
		if (root->left) traverse_R(root->right,1);
	}
}


void main()
{

	struct Node *root = new Node(1);
	root->left = new Node(2);
	root->left->left = new Node(20);
	root->left->right = new Node(3);
	root->left->right->right = new Node(4);
	root->left->right->right->left = new Node(5);
	root->left->right->right->right = new Node(6);
	root->right = new Node(14);
	root->right->right = new Node(13);
	root->right->right->right = new Node(21);
	root->right->left = new Node(10);
	root->right->left->left = new Node(9);
	root->right->left->left->left = new Node(7);
	root->right->left->left->right = new Node(8);
	root->right->right->left = new Node(12);
	root->right->right->left->right = new Node(11);

	traverse(root);

}