Reverse a binary tree.

Reverse Binary Tree.cpp

#include <iostream>
#include <vector>
#include <queue>

class Node {
public:
	int data;
	Node* left, * right;
	Node(int data) {
		this->data = data;
		left = right = NULL;
	}
};

void reverseBinaryTree(Node*& tree) {
	if (tree == 0)
		return;

	std::swap(tree->left, tree->right);

	reverseBinaryTree(tree->left);
	reverseBinaryTree(tree->right);
}

Node* insert(Node* root, int data) {
	if (root == NULL) {
		return new Node(data);
	}
	else {
		Node* cur;
		if (root->left == NULL) {
			cur = insert(root->left, data);
			root->left = cur;
		}
		else {
			cur = insert(root->right, data);
			root->right = cur;
		}

		return root;
	}
}

void printTree(Node* root) {
	if (root == 0)
		return;

	std::queue<Node*> q;

	q.push(root);

	while (q.empty() == false) {
		Node* node = q.front();
		std::cout << node->data << " ";
		q.pop();

		if (node->left != NULL)
			q.push(node->left);
		if (node->right != NULL)
			q.push(node->right);
	}

	std::cout << std::endl;
}

int main(int argc, char const* argv[])
{
	std::vector<int> data = { 1,2,3,4,5,6,7,8,9 };
	int size = data.size();

	Node* bTree = NULL;

	int i = 0;
	while (i < size)
		bTree = insert(bTree, data[i++]);

	printTree(bTree);
	reverseBinaryTree(bTree);
	printTree(bTree);

	return 0;
}