Print all even nodes of Binary Search Tree

Last Updated : 06 Sep, 2022

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

Examples:

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

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

Approach: Traverse the Binary Search tree and check if current node's value is even. If yes then print it otherwise skip that node.

Below is the implementation of the above Approach:

C++

// C++ program to print all even node of BST
#include <bits/stdc++.h>
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);
        cout << 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 even nodes
void evenNode(Node* root)
{
    if (root != NULL) {
        evenNode(root->left);
        // if node is even then print it
        if (root->key % 2 == 0)
            cout << root->key << " ";
        evenNode(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);

    evenNode(root);

    return 0;
}

Java

// Java program to print all even 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 even nodes 
static void evenNode(Node root) 
{ 
    if (root != null) { 
        evenNode(root.left); 
        // if node is even then print it 
        if (root.key % 2 == 0) 
            System.out.print(root.key + " "); 
        evenNode(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); 

    evenNode(root); 

}
}

Python3

# Python3 program to print all even 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) 
        printf("%d ", root.key) 
        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 evenNode(root) :

    if (root != None): 
        evenNode(root.left) 
        
        # if node is even then print it 
        if (root.key % 2 == 0):
            print(root.key, end = " ") 
        evenNode(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) 

    evenNode(root) 

# This code is contributed by
# Shubham Singh(SHUBHAMSINGH10)

// C# program to print all even node of BST 
using System;

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 even nodes 
    static void evenNode(Node root) 
    { 
        if (root != null)
        { 
            evenNode(root.left); 
            
            // if node is even then print it 
            if (root.key % 2 == 0) 
                Console.Write(root.key + " "); 
            evenNode(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); 

        evenNode(root); 
    } 
} 

// This code has been contributed 
// by PrinciRaj1992

JavaScript

<script>

// JavaScript program to print all even node of BST 

// create Tree 
     class Node {
            constructor() {
                this.key = 0;
                this.left = null;
                this.right = null;
            }
        }
     

// A utility function to create a new BST node 
function newNode(item) 
{ 
    var temp = new Node(); 
    temp.key = item; 
    temp.left = null;
    temp.right = null; 
    return temp; 
} 

// A utility function to do inorder traversal of BST 
function inorder(root) 
{ 
    if (root != null) { 
        inorder(root.left); 
        document.write(root.key + " "); 
        inorder(root.right); 
    } 
} 

/* A utility function to insert a new node 
with given key in BST */
function insert(node , 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 even nodes 
function evenNode(root) 
{ 
    if (root != null) { 
        evenNode(root.left); 
        // if node is even then print it 
        if (root.key % 2 == 0) 
            document.write(root.key + " "); 
        evenNode(root.right); 
    } 
} 

// Driver Code 
    /* Let us create following BST 
    5 
    / \ 
    3     7 
    / \ / \ 
    2 4 6 8 */
    var 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); 

    evenNode(root); 

// This code contributed by aashish1995 

</script>

Output

2 4 6 8

Complexity Analysis:

Time Complexity: O(N)
- Here N is the number of nodes and as we have to visit every node the time complexity is O(N).
Auxiliary Space: O(h)
- Here h is the height of the tree and extra space is used in recursion call stack.

Print Levels of all nodes in a Binary Tree

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Print all even nodes of Binary Search Tree

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