# Check if two nodes in a Binary Tree are siblings

Last Updated : 13 Sep, 2023

Given a binary tree and two nodes, the task is to check if the nodes are siblings of each other or not.

Two nodes are said to be siblings if they are present at the same level, and their parents are the same.

Examples:

`Input :        1      /  \     2    3    / \  / \   4   5 6  7First node is 4 and Second node is 6.Output : No, they are not siblings.Input :         1        /  \       5    6      /    /  \     7     3   4First node is 3 and Second node is 4Output : Yes`

Approach: On observing carefully, it can be concluded that any node in a binary tree can have maximum of two child nodes. So, since the parent of two siblings must be same, so the idea is to simply traverse the tree and for every node check if the two given nodes are its children. If it is true for any node in the tree then print YES otherwise print NO.

Below is the implementation of the above approach:

## C++

 `// C++ program to check if two nodes are` `// siblings`   `#include ` `using` `namespace` `std;`   `// Binary Tree Node` `struct` `Node {` `    ``int` `data;` `    ``Node *left, *right;` `};`   `// Utility function to create a new node` `struct` `Node* newNode(``int` `data)` `{` `    ``struct` `Node* node = ``new` `Node;` `    ``node->data = data;` `    ``node->left = node->right = NULL;`   `    ``return` `(node);` `}`   `// Function to find out if two nodes are siblings` `bool` `CheckIfNodesAreSiblings(Node* root, ``int` `data_one,` `                             ``int` `data_two)` `{` `    ``if` `(!root)` `        ``return` `false``;`   `    ``// Compare the two given nodes with` `    ``// the childrens of current node` `    ``if` `(root->left && root->right) {` `        ``int` `left = root->left->data;` `        ``int` `right = root->right->data;`   `        ``if` `(left == data_one && right == data_two)` `            ``return` `true``;` `        ``else` `if` `(left == data_two && right == data_one)` `            ``return` `true``;` `    ``}`   `    ``// Check for left subtree` `    ``if` `(root->left)` `        ``if` `(CheckIfNodesAreSiblings(root->left, data_one,` `                                    ``data_two))` `            ``return` `true``;`   `    ``// Check for right subtree` `    ``if` `(root->right)` `        ``if` `(CheckIfNodesAreSiblings(root->right, data_one,` `                                    ``data_two))` `            ``return` `true``;` `    ``return` `false``;` `}`   `// Driver code` `int` `main()` `{`   `    ``struct` `Node* root = newNode(1);` `    ``root->left = newNode(2);` `    ``root->right = newNode(3);` `    ``root->left->left = newNode(4);` `    ``root->right->left = newNode(5);` `    ``root->right->right = newNode(6);` `    ``root->left->left->right = newNode(7);`   `    ``int` `data_one = 5;` `    ``int` `data_two = 6;`   `    ``if` `(CheckIfNodesAreSiblings(root, data_one, data_two))` `        ``cout << ``"YES"``;` `    ``else` `        ``cout << ``"NO"``;`   `    ``return` `0;` `}`

## Java

 `// Java program to check if two nodes` `// are siblings` `import` `java.util.*;`   `class` `GFG {`   `    ``// Binary Tree Node` `    ``static` `class` `Node {` `        ``int` `data;` `        ``Node left, right;` `    ``};`   `    ``// Utility function to create a` `    ``// new node` `    ``static` `Node newNode(``int` `data)` `    ``{` `        ``Node node = ``new` `Node();` `        ``node.data = data;` `        ``node.left = node.right = ``null``;`   `        ``return` `(node);` `    ``}` `    ``static` `Node root = ``null``;`   `    ``// Function to find out if two nodes are siblings` `    ``static` `boolean` `CheckIfNodesAreSiblings(Node root,` `                                           ``int` `data_one,` `                                           ``int` `data_two)` `    ``{` `        ``if` `(root == ``null``)` `            ``return` `false``;`   `        ``// Compare the two given nodes with` `        ``// the childrens of current node` `        ``if` `(root.left != ``null` `&& root.right != ``null``) {` `            ``int` `left = root.left.data;` `            ``int` `right = root.right.data;`   `            ``if` `(left == data_one && right == data_two)` `                ``return` `true``;` `            ``else` `if` `(left == data_two && right == data_one)` `                ``return` `true``;` `        ``}`   `        ``// Check for left subtree` `        ``if` `(root.left != ``null``)` `            ``if` `(CheckIfNodesAreSiblings(root.left, data_one,` `                                        ``data_two))` `                ``return` `true``;`   `        ``// Check for right subtree` `        ``if` `(root.right != ``null``)` `            ``if` `(CheckIfNodesAreSiblings(root.right,` `                                        ``data_one, data_two))` `                ``return` `true``;` `        ``return` `false``;` `    ``}`   `    ``// Driver code` `    ``public` `static` `void` `main(String[] args)` `    ``{` `        ``root = newNode(``1``);` `        ``root.left = newNode(``2``);` `        ``root.right = newNode(``3``);` `        ``root.left.left = newNode(``4``);` `        ``root.right.left = newNode(``5``);` `        ``root.right.right = newNode(``6``);` `        ``root.left.left.right = newNode(``7``);`   `        ``int` `data_one = ``5``;` `        ``int` `data_two = ``6``;`   `        ``if` `(CheckIfNodesAreSiblings(root, data_one,` `                                    ``data_two))` `            ``System.out.print(``"YES"``);` `        ``else` `            ``System.out.print(``"NO"``);` `    ``}` `}`   `// This code is contributed by Rajput-Ji`

## Python3

 `# Python3 program to check if two ` `# nodes are siblings`   `# Binary Tree Node` `class` `Node:` `    `  `    ``def` `__init__(``self``, key):` `        `  `        ``self``.data ``=` `key` `        ``self``.left ``=` `None` `        ``self``.right ``=` `None`   `# Function to find out if two nodes are siblings` `def` `CheckIfNodesAreSiblings(root, data_one,` `                                  ``data_two):` `    `  `    ``if` `(root ``=``=` `None``):` `        ``return` `False`   `    ``# Compare the two given nodes with` `    ``# the childrens of current node` `    ``ans ``=` `False` `    `  `    ``if` `(root.left !``=` `None` `and` `root.right !``=` `None``):` `        ``left ``=` `root.left.data` `        ``right ``=` `root.right.data` `        `  `        ``if` `(left ``=``=` `data_one ``and` `right ``=``=` `data_two):` `            ``return` `True` `        ``elif` `(left ``=``=` `data_two ``and` `right ``=``=` `data_one):` `            ``return` `True`   `    ``# Check for left subtree` `    ``if` `(root.left !``=` `None``):` `        ``ans ``=` `ans ``or` `CheckIfNodesAreSiblings(root.left, ` `                                       ``data_one,` `                                       ``data_two)` `                                       `  `    ``# Check for right subtree` `    ``if` `(root.right !``=` `None``):` `        ``ans ``=` `ans ``or` `CheckIfNodesAreSiblings(root.right, ` `                                       ``data_one,` `                                       ``data_two)` `        `  `    ``return` `ans    `   `# Driver code` `if` `__name__ ``=``=` `'__main__'``:` `    `  `    ``root ``=` `Node(``1``)` `    ``root.left ``=` `Node(``2``)` `    ``root.right ``=` `Node(``3``)` `    ``root.left.left ``=` `Node(``4``)` `    ``root.right.left ``=` `Node(``5``)` `    ``root.right.right ``=` `Node(``6``)` `    ``root.left.left.right ``=` `Node(``7``)`   `    ``data_one ``=` `5` `    ``data_two ``=` `6`   `    ``if` `(CheckIfNodesAreSiblings(root, ` `                                ``data_one, ` `                                ``data_two)):` `        ``print``(``"YES"``)` `    ``else``:` `        ``print``(``"NO"``)`   `# This code is contributed by mohit kumar 29`

## C#

 `// C# program to check if two nodes` `// are siblings` `using` `System;`   `// Binary Tree Node` `public` `class` `Node` `{` `    ``public` `int` `data;` `    ``public` `Node left, right;` `    `  `    ``// Utility function to create a` `    ``// new node` `    ``public` `Node(``int` `item) ` `    ``{` `        ``data = item;` `        ``left = right = ``null``;` `    ``}` `}`   `class` `GFG{` `    `  `static` `Node root = ``null``;`   `// Function to find out if two ` `// nodes are siblings` `static` `bool` `CheckIfNodesAreSiblings(Node root, ` `                                    ``int` `data_one, ` `                                    ``int` `data_two)` `{` `    ``if` `(root == ``null``)` `    ``{` `        ``return` `false``;` `    ``}` `    `  `    ``// Compare the two given nodes with` `    ``// the childrens of current node` `    ``if` `(root.left != ``null` `&& root.right != ``null``) ` `    ``{` `        ``int` `left = root.left.data;` `        ``int` `right = root.right.data;` `        `  `        ``if` `(left == data_one && right == data_two)` `        ``{` `            ``return` `true``;` `        ``}` `        ``else` `if` `(left == data_two && right == data_one)` `        ``{` `            ``return` `true``;` `        ``}` `    ``}` `    `  `    ``// Check for left subtree` `    ``if` `(root.left != ``null``)` `    ``{` `        ``CheckIfNodesAreSiblings(root.left, data_one,` `                                ``data_two);` `    ``}` `    `  `    ``// Check for right subtree` `    ``if` `(root.right != ``null``)` `    ``{` `        ``CheckIfNodesAreSiblings(root.right, data_one, ` `                                ``data_two);` `    ``}` `    ``return` `true``;` `}`   `// Driver code` `static` `public` `void` `Main()` `{` `    ``GFG.root = ``new` `Node(1);` `    ``GFG.root.left = ``new` `Node(2);` `    ``GFG.root.right = ``new` `Node(3);` `    ``GFG.root.left.left = ``new` `Node(4);` `    ``GFG.root.right.left = ``new` `Node(5);` `    ``GFG.root.right.right = ``new` `Node(6);` `    ``GFG.root.left.left.right = ``new` `Node(7);` `    `  `    ``int` `data_one = 5;` `    ``int` `data_two = 6;` `    `  `    ``if` `(CheckIfNodesAreSiblings(root, data_one, ` `                                ``data_two))` `    ``{` `        ``Console.WriteLine(``"YES"``);` `    ``}` `    ``else` `    ``{` `        ``Console.WriteLine(``"NO"``);` `    ``}` `}` `}`   `// This code is contributed by avanitrachhadiya2155`

## Javascript

 ``

Output

```YES

```

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