Deepest right leaf node in a binary tree | Iterative approach

Given a Binary Tree, find the deepest leaf node that is the right child of its parent. For example, consider the following tree. The deepest right leaf node is the node with the value 10.

Examples:

```Input :
1
/   \
2     3
\   /  \
4 5    6
\    \
7    8
/      \
9        10

Output : 10```

The idea is similar to Method 2 of level order traversal

Traverse the tree level by level and while pushing right child to queue, check if it is leaf node, if it’s leaf node, then update the result and since we are traversing the level by level, the last stored right leaf will be the deepest right leaf node.

Algorithm:

• Create a queue for level order traversal.
• Push the root node into the queue.
• Initialize a variable named result to NULL.
• Traverse the tree level by level using the queue until the queue is empty.
• For each node, first check if it has a left child. If yes, then push it into the queue.
• Then check if it has a right child. If yes, then push it into the queue.
• If the node has a right child and it is a leaf node (i.e., both its left and right child are NULL), then update the result variable with this node.
• Once the traversal is complete, result will hold the deepest right leaf node of the binary tree.
• Return result.

Implementation:

C++

 `// CPP program to find deepest right leaf``// node of binary tree` `#include ` `using` `namespace` `std;` `// tree node``struct` `Node {``    ``int` `data;``    ``Node *left, *right;``};` `// returns a new tree Node``Node* newNode(``int` `data)``{``    ``Node* temp = ``new` `Node();``    ``temp->data = data;``    ``temp->left = temp->right = NULL;``    ``return` `temp;``}` `// return the deepest right leaf node``// of binary tree``Node* getDeepestRightLeafNode(Node* root)``{``    ``if` `(!root)``        ``return` `NULL;` `    ``// create a queue for level order traversal``    ``queue q;``    ``q.push(root);` `    ``Node* result = NULL;` `    ``// traverse until the queue is empty``    ``while` `(!q.empty()) {``        ``Node* temp = q.front();``        ``q.pop();` `        ``if` `(temp->left) {``            ``q.push(temp->left);``        ``}` `        ``// Since we go level by level, the last``        ``// stored right leaf node is deepest one``        ``if` `(temp->right) {``            ``q.push(temp->right);``            ``if` `(!temp->right->left && !temp->right->right)``                ``result = temp->right;``        ``}``    ``}``    ``return` `result;``}` `// driver program``int` `main()``{``    ``// construct a tree``    ``Node* root = newNode(1);``    ``root->left = newNode(2);``    ``root->right = newNode(3);``    ``root->left->right = newNode(4);``    ``root->right->left = newNode(5);``    ``root->right->right = newNode(6);``    ``root->right->left->right = newNode(7);``    ``root->right->right->right = newNode(8);``    ``root->right->left->right->left = newNode(9);``    ``root->right->right->right->right = newNode(10);` `    ``Node* result = getDeepestRightLeafNode(root);``    ``if` `(result)``        ``cout << ``"Deepest Right Leaf Node :: "``             ``<< result->data << endl;``    ``else``        ``cout << ``"No result, right leaf not found\n"``;``    ``return` `0;``}`

Java

 `// Java program to find deepest right leaf``// node of binary tree``import` `java.util.*;` `class` `GFG``{`  `// tree node``static` `class` `Node ``{``    ``int` `data;``    ``Node left, right;``};` `// returns a new tree Node``static` `Node newNode(``int` `data)``{``    ``Node temp = ``new` `Node();``    ``temp.data = data;``    ``temp.left = temp.right = ``null``;``    ``return` `temp;``}` `// return the deepest right leaf node``// of binary tree``static` `Node getDeepestRightLeafNode(Node root)``{``    ``if` `(root == ``null``)``        ``return` `null``;` `    ``// create a queue for level order traversal``    ``Queue q = ``new` `LinkedList<>();``    ``q.add(root);` `    ``Node result = ``null``;` `    ``// traverse until the queue is empty``    ``while` `(!q.isEmpty()) ``    ``{``        ``Node temp = q.peek();``        ``q.poll();` `        ` `        ``if` `(temp.left != ``null``)``        ``{``            ``q.add(temp.left);``        ``}``        ` `        ``// Since we go level by level, the last ``        ``// stored right leaf node is deepest one ``        ``if` `(temp.right != ``null``)``        ``{``            ``q.add(temp.right);``            ``if` `(temp.right.left == ``null` `&& temp.right.right == ``null``)``                ``result = temp.right;``        ``}``    ``}``    ``return` `result;``}` `// Driver code``public` `static` `void` `main(String[] args) ``{``    ` `    ``// construct a tree``    ``Node root = newNode(``1``);``    ``root.left = newNode(``2``);``    ``root.right = newNode(``3``);``    ``root.left.right = newNode(``4``);``    ``root.right.left = newNode(``5``);``    ``root.right.right = newNode(``6``);``    ``root.right.left.right = newNode(``7``);``    ``root.right.right.right = newNode(``8``);``    ``root.right.left.right.left = newNode(``9``);``    ``root.right.right.right.right = newNode(``10``);` `    ``Node result = getDeepestRightLeafNode(root);``    ``if` `(result != ``null``)``        ``System.out.println(``"Deepest Right Leaf Node :: "``            ``+ result.data);``    ``else``        ``System.out.println(``"No result, right leaf not found\n"``);``    ``}``}` `/* This code is contributed by PrinciRaj1992 */`

Python3

 `# Python3 program to find closest ``# value in Binary search Tree` `_MIN ``=` `-``2147483648``_MAX ``=` `2147483648` `# Helper function that allocates a new ``# node with the given data and None  ``# left and right pointers.                                     ``class` `newnode: ` `    ``# Constructor to create a new node ``    ``def` `__init__(``self``, data): ``        ``self``.data ``=` `data ``        ``self``.left ``=` `None``        ``self``.right ``=` `None` `# utility function to return level ``# of given node``def` `getDeepestRightLeafNode(root) :` `    ``if` `(``not` `root):``        ``return` `None` `    ``# create a queue for level ``    ``# order traversal ``    ``q ``=` `[] ``    ``q.append(root) ` `    ``result ``=` `None` `    ``# traverse until the queue is empty ``    ``while` `(``len``(q)): ``        ``temp ``=` `q[``0``] ``        ``q.pop(``0``) ` `        ``if` `(temp.left):``            ``q.append(temp.left) ``        ` `        ``# Since we go level by level, the last ``        ``# stored right leaf node is deepest one ``        ``if` `(temp.right): ``            ``q.append(temp.right) ``            ``if` `(``not` `temp.right.left ``and``                ``not` `temp.right.right): ``                ``result ``=` `temp.right ` `    ``return` `result` `# Driver Code ``if` `__name__ ``=``=` `'__main__'``:``    ` `    ``# create a binary tree ``    ``root ``=` `newnode(``1``) ``    ``root.left ``=` `newnode(``2``) ``    ``root.right ``=` `newnode(``3``) ``    ``root.left.right ``=` `newnode(``4``)``    ``root.right.left ``=` `newnode(``5``) ``    ``root.right.right ``=` `newnode(``6``)``    ``root.right.left.right ``=` `newnode(``7``)``    ``root.right.right.right ``=` `newnode(``8``)``    ``root.right.left.right.left ``=` `newnode(``9``)``    ``root.right.right.right.right ``=` `newnode(``10``) ` `    ``result ``=` `getDeepestRightLeafNode(root)``    ``if` `result:``        ``print``(``"Deepest Right Leaf Node ::"``,``                               ``result.data)``    ``else``:``        ``print``(``"No result, right leaf not found"``)``        ` `# This code is contributed by``# Shubham Singh(SHUBHAMSINGH10)`

C#

 `// C# program to find deepest right leaf``// node of binary tree``using` `System;``using` `System.Collections.Generic; ``    ` `class` `GFG``{`  `// tree node``public` `class` `Node ``{``    ``public` `int` `data;``    ``public` `Node left, right;``};` `// returns a new tree Node``static` `Node newNode(``int` `data)``{``    ``Node temp = ``new` `Node();``    ``temp.data = data;``    ``temp.left = temp.right = ``null``;``    ``return` `temp;``}` `// return the deepest right leaf node``// of binary tree``static` `Node getDeepestRightLeafNode(Node root)``{``    ``if` `(root == ``null``)``        ``return` `null``;` `    ``// Create a queue for level order traversal``    ``Queue q = ``new` `Queue();``    ``q.Enqueue(root);` `    ``Node result = ``null``;` `    ``// Traverse until the queue is empty``    ``while` `(q.Count!=0) ``    ``{``        ``Node temp = q.Peek();``        ``q.Dequeue();` `        ` `        ``if` `(temp.left != ``null``)``        ``{``            ``q.Enqueue(temp.left);``        ``}``        ` `        ``// Since we go level by level, the last ``        ``// stored right leaf node is deepest one ``        ``if` `(temp.right != ``null``)``        ``{``            ``q.Enqueue(temp.right);``            ``if` `(temp.right.left == ``null` `&& temp.right.right == ``null``)``                ``result = temp.right;``        ``}``    ``}``    ``return` `result;``}` `// Driver code``public` `static` `void` `Main(String[] args) ``{``    ` `    ``// construct a tree``    ``Node root = newNode(1);``    ``root.left = newNode(2);``    ``root.right = newNode(3);``    ``root.left.right = newNode(4);``    ``root.right.left = newNode(5);``    ``root.right.right = newNode(6);``    ``root.right.left.right = newNode(7);``    ``root.right.right.right = newNode(8);``    ``root.right.left.right.left = newNode(9);``    ``root.right.right.right.right = newNode(10);` `    ``Node result = getDeepestRightLeafNode(root);``    ``if` `(result != ``null``)``        ``Console.WriteLine(``"Deepest Right Leaf Node :: "``            ``+ result.data);``    ``else``        ``Console.WriteLine(``"No result, right leaf not found\n"``);``}``}` `// This code is contributed by Princi Singh`

Javascript

 ``

Output
`Deepest Right Leaf Node :: 10`

Time Complexity: O(n)

Auxiliary Space: O(n)  because using queue

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