bttransversal.cpp

#include <iostream>
using namespace std;

// Data structure to store a Binary Tree node
struct Node
{
    int key;
    Node *left, *right;

    Node(int key)
    {
        this->key = key;
        this->left = this->right = nullptr;
    }
};

// Function to print all nodes of a given level from left to right
bool printLevel(Node* root, int level)
{
    if (root == nullptr)
        return false;
    if (level == 1)
    {
        cout << root->key << " ";

        // return true if at-least one node is present at given level
        return true;
    }
    bool left = printLevel(root->left, level - 1);
    bool right = printLevel(root->right, level - 1);
//until both left and right are empty
    return left || right;
}

// Function to print level order traversal of given binary tree
void levelOrderTraversal(Node* root)
{
    // start from level 1 -- till height of the tree
    int level = 1;

    // run till printLevel() returns false
    while (printLevel(root, level))
        level++;
}

void preOrderTraversal(Node* root){
	if (root==NULL)
		return;
	cout<<root->key<<" ";
	preOrderTraversal(root->left);
	preOrderTraversal(root->right);
}

// main function
int main()
{
    Node* root = nullptr;

    root = new Node(15);
    root->left = new Node(10);
    root->right = new Node(20);
    root->left->left = new Node(8);
    root->left->right = new Node(12);
    root->right->left = new Node(16);
    root->right->right = new Node(25);

    levelOrderTraversal(root);
    cout<<"\n";
    preOrderTraversal(root);

    return 0;
}