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Print all odd nodes of Binary Search Tree
• Difficulty Level : Medium
• Last Updated : 31 Oct, 2019

Given a binary search tree. The task is to print all odd nodes of the binary search tree.

Examples:

```Input :
5
/   \
3     7
/ \   / \
2   4 6   8
Output : 3 5 7

Input :
14
/   \
12    17
/ \   / \
8  13 16   19
Output : 13 17 19
```

Approach: Traverse the Binary Search tree using any of the tree traversals and check if current node’s value is odd. If yes then print it otherwise skip that node.

Below is the implementation of the above Approach:

## C++

 `// C++ program to print all odd node of BST``#include ``using` `namespace` `std;`` ` `// create Tree``struct` `Node {``    ``int` `key;``    ``struct` `Node *left, *right;``};`` ` `// A utility function to create a new BST node``Node* newNode(``int` `item)``{``    ``Node* temp = ``new` `Node;``    ``temp->key = item;``    ``temp->left = temp->right = NULL;``    ``return` `temp;``}`` ` `// A utility function to do inorder traversal of BST``void` `inorder(Node* root)``{``    ``if` `(root != NULL) {``        ``inorder(root->left);``        ``printf``(``"%d "``, root->key);``        ``inorder(root->right);``    ``}``}`` ` `/* A utility function to insert a new node ``   ``with given key in BST */``Node* insert(Node* node, ``int` `key)``{``    ``/* If the tree is empty, return a new node */``    ``if` `(node == NULL)``        ``return` `newNode(key);`` ` `    ``/* Otherwise, recur down the tree */``    ``if` `(key < node->key)``        ``node->left = insert(node->left, key);``    ``else``        ``node->right = insert(node->right, key);`` ` `    ``/* return the (unchanged) node pointer */``    ``return` `node;``}`` ` `// Function to print all odd nodes``void` `oddNode(Node* root)``{``    ``if` `(root != NULL) {``        ``oddNode(root->left);`` ` `        ``// if node is odd then print it``        ``if` `(root->key % 2 != 0)``            ``printf``(``"%d "``, root->key);`` ` `        ``oddNode(root->right);``    ``}``}`` ` `// Driver Code``int` `main()``{``    ``/* Let us create following BST  ``        ``5  ``      ``/  \  ``     ``3    7  ``    ``/ \  / \  ``    ``2 4  6 8 */``    ``Node* root = NULL;``    ``root = insert(root, 5);``    ``root = insert(root, 3);``    ``root = insert(root, 2);``    ``root = insert(root, 4);``    ``root = insert(root, 7);``    ``root = insert(root, 6);``    ``root = insert(root, 8);`` ` `    ``oddNode(root);`` ` `    ``return` `0;``}`

## Java

 `// Java program to print all odd node of BST ``class` `GfG { `` ` `// create Tree ``static` `class` `Node { ``    ``int` `key; ``    ``Node left, right; ``} `` ` `// A utility function to create a new BST node ``static` `Node newNode(``int` `item) ``{ ``    ``Node temp = ``new` `Node(); ``    ``temp.key = item; ``    ``temp.left = ``null``;``    ``temp.right = ``null``; ``    ``return` `temp; ``} `` ` `// A utility function to do inorder traversal of BST ``static` `void` `inorder(Node root) ``{ ``    ``if` `(root != ``null``) { ``        ``inorder(root.left); ``        ``System.out.print(root.key + ``" "``); ``        ``inorder(root.right); ``    ``} ``} `` ` `/* A utility function to insert a new node ``with given key in BST */``static` `Node insert(Node node, ``int` `key) ``{ ``    ``/* If the tree is empty, return a new node */``    ``if` `(node == ``null``) ``        ``return` `newNode(key); `` ` `    ``/* Otherwise, recur down the tree */``    ``if` `(key < node.key) ``        ``node.left = insert(node.left, key); ``    ``else``        ``node.right = insert(node.right, key); `` ` `    ``/* return the (unchanged) node pointer */``    ``return` `node; ``} `` ` `// Function to print all odd nodes ``static` `void` `oddNode(Node root) ``{ ``    ``if` `(root != ``null``) { ``        ``oddNode(root.left); `` ` `        ``// if node is odd then print it ``        ``if` `(root.key % ``2` `!= ``0``) ``            ``System.out.print(root.key + ``" "``); `` ` `        ``oddNode(root.right); ``    ``} ``} `` ` `// Driver Code ``public` `static` `void` `main(String[] args) ``{ ``    ``/* Let us create following BST ``        ``5 ``    ``/ \ ``    ``3 7 ``    ``/ \ / \ ``    ``2 4 6 8 */``    ``Node root = ``null``; ``    ``root = insert(root, ``5``); ``    ``root = insert(root, ``3``); ``    ``root = insert(root, ``2``); ``    ``root = insert(root, ``4``); ``    ``root = insert(root, ``7``); ``    ``root = insert(root, ``6``); ``    ``root = insert(root, ``8``); `` ` `    ``oddNode(root); `` ` `} ``} `

## Python3

 `# Python3 program to print all odd ``# node of BST `` ` `# create Tree ``# to create a new BST node ``class` `newNode: `` ` `    ``# Construct to create a new node ``    ``def` `__init__(``self``, key): ``        ``self``.key ``=` `key``        ``self``.left ``=` `None``        ``self``.right ``=` `None`` ` `# A utility function to do inorder ``# traversal of BST ``def` `inorder( root) :`` ` `    ``if` `(root !``=` `None``): ``        ``inorder(root.left) ``        ``print``(root.key, end ``=` `" "``) ``        ``inorder(root.right) ``     ` `""" A utility function to insert a ``new node with given key in BST """``def` `insert(node, key): `` ` `    ``""" If the tree is empty, ``    ``return a new node """``    ``if` `(node ``=``=` `None``): ``        ``return` `newNode(key) `` ` `    ``""" Otherwise, recur down the tree """``    ``if` `(key < node.key): ``        ``node.left ``=` `insert(node.left, key) ``    ``else``:``        ``node.right ``=` `insert(node.right, key) `` ` `    ``""" return the (unchanged) node pointer """``    ``return` `node `` ` `# Function to print all even nodes ``def` `oddNode(root) :`` ` `    ``if` `(root !``=` `None``): ``        ``oddNode(root.left) ``         ` `        ``# if node is even then print it ``        ``if` `(root.key ``%` `2` `!``=` `0``):``            ``print``(root.key, end ``=` `" "``) ``        ``oddNode(root.right) `` ` `# Driver Code ``if` `__name__ ``=``=` `'__main__'``:``     ` `    ``""" Let us create following BST ``    ``5 ``    ``/ \ ``    ``3 7 ``    ``/ \ / \ ``    ``2 4 6 8 """``    ``root ``=` `None``    ``root ``=` `insert(root, ``5``) ``    ``root ``=` `insert(root, ``3``) ``    ``root ``=` `insert(root, ``2``) ``    ``root ``=` `insert(root, ``4``) ``    ``root ``=` `insert(root, ``7``) ``    ``root ``=` `insert(root, ``6``) ``    ``root ``=` `insert(root, ``8``) `` ` `    ``oddNode(root) `` ` `# This code is contributed by``# Shubham Singh(SHUBHAMSINGH10)`

## C#

 `// C# program to print all odd node of BST``using` `System;`` ` `public` `class` `GfG ``{ `` ` `// create Tree ``class` `Node ``{ ``    ``public` `int` `key; ``    ``public` `Node left, right; ``} `` ` `// A utility function to create a new BST node ``static` `Node newNode(``int` `item) ``{ ``    ``Node temp = ``new` `Node(); ``    ``temp.key = item; ``    ``temp.left = ``null``; ``    ``temp.right = ``null``; ``    ``return` `temp; ``} `` ` `// A utility function to do ``// inorder traversal of BST ``static` `void` `inorder(Node root) ``{ ``    ``if` `(root != ``null``)``    ``{ ``        ``inorder(root.left); ``        ``Console.Write(root.key + ``" "``); ``        ``inorder(root.right); ``    ``} ``} `` ` `/* A utility function to insert a new node ``with given key in BST */``static` `Node insert(Node node, ``int` `key) ``{ ``    ``/* If the tree is empty, return a new node */``    ``if` `(node == ``null``) ``        ``return` `newNode(key); `` ` `    ``/* Otherwise, recur down the tree */``    ``if` `(key < node.key) ``        ``node.left = insert(node.left, key); ``    ``else``        ``node.right = insert(node.right, key); `` ` `    ``/* return the (unchanged) node pointer */``    ``return` `node; ``} `` ` `// Function to print all odd nodes ``static` `void` `oddNode(Node root) ``{ ``    ``if` `(root != ``null``) ``    ``{ ``        ``oddNode(root.left); `` ` `        ``// if node is odd then print it ``        ``if` `(root.key % 2 != 0) ``            ``Console.Write(root.key + ``" "``); `` ` `        ``oddNode(root.right); ``    ``} ``} `` ` `// Driver Code ``public` `static` `void` `Main(String[] args) ``{ ``    ``/* Let us create following BST ``        ``5 ``    ``/ \ ``    ``3 7 ``    ``/ \ / \ ``    ``2 4 6 8 */``    ``Node root = ``null``; ``    ``root = insert(root, 5); ``    ``root = insert(root, 3); ``    ``root = insert(root, 2); ``    ``root = insert(root, 4); ``    ``root = insert(root, 7); ``    ``root = insert(root, 6); ``    ``root = insert(root, 8); `` ` `    ``oddNode(root); `` ` `} ``} `` ` `// This code has been contributed ``// by PrinciRaj1992`
Output:
```3 5 7
```

Time Complexity : O(n) where n is no. Of nodes

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