Related Articles

# Print all nodes between two given levels in Binary Tree

• Difficulty Level : Medium
• Last Updated : 30 Jun, 2021

Given a binary tree, print all nodes between two given levels in a binary tree. Print the nodes level wise, i.e., the nodes for any level should be printed from left to right. In the above tree, if the starting level is 2 and the ending level is 3 then the solution should print:

```2 3
4 5 6 7 ```

Note: Level number starts with 1. That is, the root node is at level 1.

Prerequisite: Level order Traversal.
The idea is to do level order traversal of the tree using a queue and keep track of the current level. If the current level lies between the starting and ending level then print the nodes at that level.
Algorithm:

```levelordertraverse (root, startLevel, endLevel)
q -> empty queue
q.enqueue (root)
level -> 0
while (not q.isEmpty())
size -> q.size()
level = level + 1
while (size)
node -> q.dequeue()
if (level between startLevel and endevel)
print (node)
if(node.leftnull)
q.enqueue (node. left)
if(node.leftnull)
q.enqueue(node.right)
size =size -1```

Below is the implementation of the above algorithm:

## C++

 `// C++ program for Print all nodes``// between two given levels in``// a binary tree``#include``using` `namespace` `std;` `// Class containing left and right``// child of current node and key value``struct` `tree``{` `    ``int` `data;``    ``tree *left, *right;``};``struct` `tree* newNode(``int` `x)``{``    ``tree* temp = ``new` `tree;``    ``temp->data = x;``    ``temp->left = temp->right = NULL;``}` `// Iterative function to print all``// nodes between two given``// levels in a binary tree``void` `printNodes(tree* root, ``int` `start, ``int` `end)``{``    ``if` `(root == NULL)``    ``{``        ``return``;``    ``}` `    ``// create an empty queue and``    ``// enqueue root node``    ``queue queue ;``    ``queue.push(root);` `    ``// pointer to store current node``    ``tree *curr = NULL;` `    ``// maintains level of current node``    ``int` `level = 0;` `    ``// run till queue is not empty``    ``while` `(!queue.empty())``    ``{``        ``// increment level by 1``        ``level++;` `        ``// calculate number of nodes in``        ``// current level``        ``int` `size = queue.size();` `        ``// process every node of current level``        ``// and enqueue their non-empty left``        ``// and right child to queue``        ``while` `(size != 0)``        ``{``            ``curr = queue.front();``            ``queue.pop();` `            ``// print the node if its level is``            ``// between given levels``            ``if` `(level >= start && level <= end)``            ``{``                ``cout << curr->data << ``" "``;``            ``}``            ``if` `(curr->left != NULL)``            ``{``                ``queue.push(curr->left);``            ``}` `            ``if` `(curr->right != NULL)``            ``{``                ``queue.push(curr->right);``            ``}``            ``size--;``        ``}` `        ``if` `(level >= start && level <= end)``        ``{``            ``cout << (``"\n"``);``        ``};``    ``}``}` `// Driver Code``int` `main()``{``    ` `    ``tree *root = newNode(1);``    ``root->left = newNode(2);``    ``root->right = newNode(3);``    ``root->left->left = newNode(4);``    ``root->left->right = newNode(5);``    ``root->right->left = newNode(6);``    ``root->right->right = newNode(7);` `    ``/* Constructed binary tree is``        ``1``    ``/ \``    ``2 3``    ``/ \ / \``    ``4 5 6 7 */` `    ``int` `start = 2, end = 3;` `    ``printNodes(root, start, end);``}` `// This code is contributed by Rajput-Ji`

## Java

 `// Java program for Print all nodes``// between two given levels in``// a binary tree` `import` `java.util.LinkedList;``import` `java.util.Queue;` `public` `class` `BinaryTree {` `    ``// Class containing left and right``    ``// child of current node and key value``    ``static` `class` `Node {` `        ``int` `data;``        ``Node left, right;` `        ``public` `Node(``int` `item)``        ``{``            ``data = item;``            ``left = right = ``null``;``        ``}``    ``}` `    ``// Root of the Binary Tree``    ``Node root;``    ``public` `BinaryTree()``    ``{``        ``root = ``null``;``    ``}` `    ``// Iterative function to print all``    ``// nodes between two given``    ``// levels in a binary tree``    ``void` `printNodes(Node root, ``int` `start, ``int` `end)``    ``{``        ``if` `(root == ``null``) {``            ``return``;``        ``}` `        ``// create an empty queue and``        ``// enqueue root node``        ``Queue queue = ``new` `LinkedList();``        ``queue.add(root);` `        ``// pointer to store current node``        ``Node curr = ``null``;` `        ``// maintains level of current node``        ``int` `level = ``0``;` `        ``// run till queue is not empty``        ``while` `(!queue.isEmpty()) {``            ``// increment level by 1``            ``level++;` `            ``// calculate number of nodes in``            ``// current level``            ``int` `size = queue.size();` `            ``// process every node of current level``            ``// and enqueue their non-empty left``            ``// and right child to queue``            ``while` `(size != ``0``) {``                ``curr = queue.poll();` `                ``// print the node if its level is``                ``// between given levels``                ``if` `(level >= start && level <= end) {``                    ``System.out.print(curr.data + ``" "``);``                ``}``                ``if` `(curr.left != ``null``) {``                    ``queue.add(curr.left);``                ``}` `                ``if` `(curr.right != ``null``) {``                    ``queue.add(curr.right);``                ``}``                ``size--;``            ``}` `            ``if` `(level >= start && level <= end) {``                ``System.out.println(``""``);``            ``};``        ``}``    ``}` `    ``// Driver Code``    ``public` `static` `void` `main(String args[])``    ``{``        ``BinaryTree tree = ``new` `BinaryTree();``        ``tree.root = ``new` `Node(``1``);``        ``tree.root.left = ``new` `Node(``2``);``        ``tree.root.right = ``new` `Node(``3``);``        ``tree.root.left.left = ``new` `Node(``4``);``        ``tree.root.left.right = ``new` `Node(``5``);``        ``tree.root.right.left = ``new` `Node(``6``);``        ``tree.root.right.right = ``new` `Node(``7``);` `        ``/* Constructed binary tree is``             ``1``           ``/  \``          ``2    3``         ``/ \  / \``        ``4   5 6  7 */` `        ``int` `start = ``2``, end = ``3``;` `        ``tree.printNodes(tree.root, start, end);``    ``}``}`

## Python3

 `# Python3 program for Print all nodes``# between two given levels in``# a binary tree` `# Helper function that allocates a new``# node with the given data and None``# left and right poers.                                ``class` `newNode:` `    ``# Construct to create a new node``    ``def` `__init__(``self``, key):``        ``self``.data ``=` `key``        ``self``.left ``=` `None``        ``self``.right ``=` `None` `# Iterative function to print all``# nodes between two given``# levels in a binary tree``def` `prNodes(root, start, end):``    ` `    ``if` `(root ``=``=` `None``):``        ``return` `    ``# create an empty queue and``    ``# enqueue root node``    ``q ``=` `[]``    ``q.append(root)` `    ``# poer to ste current node``    ``curr ``=` `None` `    ``# maains level of current node``    ``level ``=` `0` `    ``# run till queue is not empty``    ``while` `(``len``(q)):``        ` `        ``# increment level by 1``        ``level ``+``=` `1` `        ``# calculate number of nodes in``        ``# current level``        ``size ``=` `len``(q)` `        ``# process every node of current level``        ``# and enqueue their non-empty left``        ``# and right child to queue``        ``while` `(size !``=` `0``) :``            ``curr ``=` `q[``0``]``            ``q.pop(``0``)` `            ``# print the node if its level is``            ``# between given levels``            ``if` `(level >``=` `start ``and` `level <``=` `end) :``                ``print``(curr.data, end ``=` `" "``)``            ` `            ``if` `(curr.left !``=` `None``) :``                ``q.append(curr.left)``            ` `            ``if` `(curr.right !``=` `None``) :``                ``q.append(curr.right)``            ` `            ``size ``-``=` `1``        ` `        ``if` `(level >``=` `start ``and` `level <``=` `end) :``            ``print``("")``            ` `# Driver Code``if` `__name__ ``=``=` `'__main__'``:``    ` `    ``"""``    ``Let us create Binary Tree shown``    ``in above example """``    ``root ``=` `newNode(``1``)``    ``root.left ``=` `newNode(``2``)` `    ``root.left.left ``=` `newNode(``4``)``    ``root.left.right ``=` `newNode(``5``)``    ``root.right ``=` `newNode(``3``)``    ``root.right.right ``=` `newNode(``7``)``    ``root.right.left ``=` `newNode(``6``)``    ``start ``=` `2``    ``end ``=` `3``    ``prNodes(root, start, end)``    ` `# This code is contributed by``# Shubham Singh(SHUBHAMSINGH10)`

## C#

 `// C# program for Print all nodes``// between two given levels in``// a binary tree``using` `System;``using` `System.Collections.Generic;` `public` `class` `BinaryTree``{` `    ``// Class containing left and right``    ``// child of current node and key value``    ``public` `class` `Node``    ``{` `        ``public` `int` `data;``        ``public` `Node left, right;` `        ``public` `Node(``int` `item)``        ``{``            ``data = item;``            ``left = right = ``null``;``        ``}``    ``}` `    ``// Root of the Binary Tree``    ``Node root;` `    ``public` `BinaryTree()``    ``{``        ``root = ``null``;``    ``}` `    ``// Iterative function to print all``    ``// nodes between two given``    ``// levels in a binary tree``    ``void` `printNodes(Node root, ``int` `start, ``int` `end)``    ``{``        ``if` `(root == ``null``)``        ``{``            ``return``;``        ``}` `        ``// create an empty queue and``        ``// enqueue root node``        ``Queue queue = ``new` `Queue();``        ``queue.Enqueue(root);` `        ``// pointer to store current node``        ``Node curr = ``null``;` `        ``// maintains level of current node``        ``int` `level = 0;` `        ``// run till queue is not empty``        ``while` `(queue.Count >0)``        ``{``            ``// increment level by 1``            ``level++;` `            ``// calculate number of nodes in``            ``// current level``            ``int` `size = queue.Count;` `            ``// process every node of current level``            ``// and enqueue their non-empty left``            ``// and right child to queue``            ``while` `(size != 0)``            ``{``                ``curr = queue.Peek();``                ``queue.Dequeue();` `                ``// print the node if its level is``                ``// between given levels``                ``if` `(level >= start && level <= end)``                ``{``                    ``Console.Write(curr.data + ``" "``);``                ``}``                ``if` `(curr.left != ``null``)``                ``{``                    ``queue.Enqueue(curr.left);``                ``}` `                ``if` `(curr.right != ``null``)``                ``{``                    ``queue.Enqueue(curr.right);``                ``}``                ``size--;``            ``}` `            ``if` `(level >= start && level <= end)``            ``{``                ``Console.WriteLine(``""``);``            ``};``        ``}``    ``}` `    ``// Driver Code``    ``public` `static` `void` `Main(String []args)``    ``{``        ``BinaryTree tree = ``new` `BinaryTree();``        ``tree.root = ``new` `Node(1);``        ``tree.root.left = ``new` `Node(2);``        ``tree.root.right = ``new` `Node(3);``        ``tree.root.left.left = ``new` `Node(4);``        ``tree.root.left.right = ``new` `Node(5);``        ``tree.root.right.left = ``new` `Node(6);``        ``tree.root.right.right = ``new` `Node(7);` `        ``/* Constructed binary tree is``            ``1``        ``/ \``        ``2 3``        ``/ \ / \``        ``4 5 6 7 */``        ``int` `start = 2, end = 3;` `        ``tree.printNodes(tree.root, start, end);``    ``}``}` `// This code is contributed by 29AjayKumar`

## Javascript

 ``
Output
```2 3
4 5 6 7 ```

Attention reader! Don’t stop learning now. Get hold of all the important DSA concepts with the DSA Self Paced Course at a student-friendly price and become industry ready.  To complete your preparation from learning a language to DS Algo and many more,  please refer Complete Interview Preparation Course.

In case you wish to attend live classes with experts, please refer DSA Live Classes for Working Professionals and Competitive Programming Live for Students.

My Personal Notes arrow_drop_up