# Non-recursive program to delete an entire binary tree

• Difficulty Level : Easy
• Last Updated : 17 Jul, 2022

We have discussed recursive implementation to delete an entire binary tree here.
We strongly recommend you to minimize your browser and try this yourself first.
Now how to delete an entire tree without using recursion. This could easily be done with the help of Level Order Tree Traversal. The idea is for each dequeued node from the queue, delete it after queuing its left and right nodes (if any). The solution will work as we are traverse all the nodes of the tree level by level from top to bottom, and before deleting the parent node, we are storing its children into queue that will be deleted later.

## C++

 `/* Non-Recursive Program to delete an entire binary tree. */``#include ``using` `namespace` `std;`` ` `// A Binary Tree Node``struct` `Node``{``    ``int` `data;``    ``struct` `Node *left, *right;``};`` ` `/* Non-recursive function to delete an entire binary tree. */``void` `_deleteTree(Node *root)``{``    ``// Base Case``    ``if` `(root == NULL)``        ``return``;`` ` `    ``// Create an empty queue for level order traversal``    ``queue q;`` ` `    ``// Do level order traversal starting from root``    ``q.push(root);``    ``while` `(!q.empty())``    ``{``        ``Node *node = q.front();``        ``q.pop();`` ` `        ``if` `(node->left != NULL)``            ``q.push(node->left);``        ``if` `(node->right != NULL)``            ``q.push(node->right);`` ` `        ``free``(node);``    ``}``}`` ` `/* Deletes a tree and sets the root as NULL */``void` `deleteTree(Node** node_ref)``{``  ``_deleteTree(*node_ref);``  ``*node_ref = NULL;``}`` ` `// Utility function to create a new tree Node``Node* newNode(``int` `data)``{``    ``Node *temp = ``new` `Node;``    ``temp->data = data;``    ``temp->left = temp->right = NULL;`` ` `    ``return` `temp;``}`` ` `// Driver program to test above functions``int` `main()``{``    ``// create a binary tree``    ``Node *root =  newNode(15);``    ``root->left = newNode(10);``    ``root->right = newNode(20);``    ``root->left->left = newNode(8);``    ``root->left->right = newNode(12);``    ``root->right->left = newNode(16);``    ``root->right->right = newNode(25);`` ` `    ``//delete entire binary tree``    ``deleteTree(&root);`` ` `    ``return` `0;``}`

## Java

 `/* Non-recursive program to delete the entire binary tree */``import` `java.util.*;`` ` `// A binary tree node``class` `Node ``{``    ``int` `data;``    ``Node left, right;`` ` `    ``public` `Node(``int` `data) ``    ``{``        ``this``.data = data;``        ``left = right = ``null``;``    ``}``}`` ` `class` `BinaryTree ``{``    ``Node root;`` ` `    ``/* Non-recursive function to delete an entire binary tree. */``    ``void` `_deleteTree() ``    ``{``        ``// Base Case``        ``if` `(root == ``null``)``            ``return``;`` ` `        ``// Create an empty queue for level order traversal``        ``Queue q = ``new` `LinkedList();`` ` `        ``// Do level order traversal starting from root``        ``q.add(root);``        ``while` `(!q.isEmpty()) ``        ``{``            ``Node node = q.peek();``            ``q.poll();`` ` `            ``if` `(node.left != ``null``)``                ``q.add(node.left);``            ``if` `(node.right != ``null``)``                ``q.add(node.right);``        ``}``    ``}`` ` `    ``/* Deletes a tree and sets the root as NULL */``    ``void` `deleteTree() ``    ``{``        ``_deleteTree();``        ``root = ``null``;``    ``}`` ` `    ``// Driver program to test above functions``    ``public` `static` `void` `main(String[] args) ``    ``{``        ``// create a binary tree``        ``BinaryTree tree = ``new` `BinaryTree();``        ``tree.root = ``new` `Node(``15``);``        ``tree.root.left = ``new` `Node(``10``);``        ``tree.root.right = ``new` `Node(``20``);``        ``tree.root.left.left = ``new` `Node(``8``);``        ``tree.root.left.right = ``new` `Node(``12``);``        ``tree.root.right.left = ``new` `Node(``16``);``        ``tree.root.right.right = ``new` `Node(``25``);`` ` `        ``// delete entire binary tree``        ``tree.deleteTree();``    ``}``}`` ` `// This code has been contributed by Mayank Jaiswal(mayank_24)`

## Python3

 `# Python program to delete an entire binary tree``# using non-recursive approach`` ` `# A binary tree node``class` `Node:``     ` `    ``# A constructor to create a new node``    ``def` `__init__(``self``, data):``        ``self``.data ``=` `data ``        ``self``.left ``=` `None``        ``self``.right ``=` `None`` ` `# Non-recursive function to delete an entrie binary tree``def` `_deleteTree(root):``     ` `    ``# Base Case``    ``if` `root ``is` `None``:``        ``return` ` ` `    ``# Create a empty queue for level order traversal``    ``q ``=` `[]`` ` `    ``# Do level order traversal starting from root``    ``q.append(root)``    ``while``(``len``(q)>``0``):``        ``node ``=` `q.pop(``0``)``     ` `        ``if` `node.left ``is` `not` `None``:``            ``q.append(node.left)`` ` `        ``if` `node.right ``is` `not` `None``:``            ``q.append(node.right)`` ` `        ``node ``=` `None``    ``return` `node`` ` `# Deletes a tree and sets the root as None``def` `deleteTree(node_ref):``    ``node_ref ``=` `_deleteTree(node_ref)``    ``return` `node_ref`` ` `# Driver program to test above function`` ` `# Create a binary tree``root ``=` `Node(``15``)``root.left ``=` `Node(``10``)``root.right ``=` `Node(``20``)``root.left.left ``=` `Node(``8``)``root.left.right ``=` `Node(``12``)``root.right.left ``=` `Node(``16``)``root.right.right ``=` `Node(``25``)`` ` `# delete entire binary tree``root ``=` `deleteTree(root)`` ` ` ` `# This program is contributed by Nikhil Kumar Singh(nickzuck_007)`

## C#

 `/* Non-recursive program to delete the entire binary tree */``using` `System;``using` `System.Collections.Generic;`` ` `// A binary tree node``public` `class` `Node ``{``    ``public` `int` `data;``    ``public` `Node left, right;`` ` `    ``public` `Node(``int` `data) ``    ``{``        ``this``.data = data;``        ``left = right = ``null``;``    ``}``}`` ` `public` `class` `BinaryTree ``{``    ``Node root;`` ` `    ``/* Non-recursive function to``    ``delete an entire binary tree. */``    ``void` `_deleteTree() ``    ``{``        ``// Base Case``        ``if` `(root == ``null``)``            ``return``;`` ` `        ``// Create an empty queue for level order traversal``        ``Queue q = ``new` `Queue();`` ` `        ``// Do level order traversal starting from root``        ``q.Enqueue(root);``        ``while` `(q.Count != 0) ``        ``{``            ``Node node = q.Peek();``            ``q.Dequeue();`` ` `            ``if` `(node.left != ``null``)``                ``q.Enqueue(node.left);``            ``if` `(node.right != ``null``)``                ``q.Enqueue(node.right);``        ``}``    ``}`` ` `    ``/* Deletes a tree and sets the root as NULL */``    ``void` `deleteTree() ``    ``{``        ``_deleteTree();``        ``root = ``null``;``    ``}`` ` `    ``// Driver program to test above functions``    ``public` `static` `void` `Main(String[] args) ``    ``{``        ``// create a binary tree``        ``BinaryTree tree = ``new` `BinaryTree();``        ``tree.root = ``new` `Node(15);``        ``tree.root.left = ``new` `Node(10);``        ``tree.root.right = ``new` `Node(20);``        ``tree.root.left.left = ``new` `Node(8);``        ``tree.root.left.right = ``new` `Node(12);``        ``tree.root.right.left = ``new` `Node(16);``        ``tree.root.right.right = ``new` `Node(25);`` ` `        ``// delete entire binary tree``        ``tree.deleteTree();``    ``}``}`` ` `// This code has been contributed by 29AjayKumar`

## Javascript

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Time Complexity: O(n)

As it is a normal level order traversal and we are visiting every node just once.

Auxiliary Space: O(b)

Here b is the breadth of the tree or the maximum number of elements at any level. The extra space is required to store the elements of a level in the queue.