Delete leaf nodes with value k

Given a binary tree and value k. delete all the leaf nodes with value equal to k. If a node becomes leaf after deletion, then it should be deleted if it has value k.

Examples: 

Input :     4
         /     \
        5       5
       /  \    /
      3    1  5 

Output :    4
         /     
        5       
       /  \    
      3    1  

1. Use PostOrder traversal. 
2. When we encounter leaf nodes, then we check whether it is leaf node or not. 
3. If it is leaf node and value equal to k, then delete it. 
4. Else, Recurse for other nodes.  

Implementation:

C++

// C++ program to delete leaf nodes with
// value equal to k.
#include<bits/stdc++.h>
using namespace std;

struct Node
{
    int data;
    struct Node *left, *right;
};

struct Node* newNode(int data)
{
    struct Node* newNode = new Node;
    newNode->data = data;
    newNode->left = newNode->right = NULL;
    return (newNode);
}

// Function to delete leaf Node with value
// equal to k
Node* LeafNodesWithValueK(Node* root, int k)
{
    if (root == NULL)
        return nullptr;

    root->left = LeafNodesWithValueK(root->left, k);
    root->right = LeafNodesWithValueK(root->right, k);

    // If the node is leaf, and its
        // value is equal to k

    if (root->data == k &&
        root->left == NULL &&
        root->right == NULL)
    {
        return nullptr;
    }
    return root;
}

void postOrder(Node* root)
{
    if (root == NULL)
        return;

    cout << root->data << " ";

    postOrder(root->left);
    postOrder(root->right);
}

// Driver code
int main()
{
    struct Node* root = newNode(4);
    root->left = newNode(5);
    root->right = newNode(5);
    root->left->left = newNode(3);
    root->left->right = newNode(1);
    root->right->right = newNode(5);

    cout << "Nodes in postorder before deletion \n";
    postOrder(root);
    cout << "\n";

    int k = 5;
    LeafNodesWithValueK(root, k);
    cout << "Nodes in post order after "
            "required deletion \n";
    postOrder(root);
    return 0;
}

// This code is contributed by Stream_Cipher

Java

// Java program to delete leaf nodes with
// value equal to k.

class Node {
    int data;
    Node left;
    Node right;

    public Node(int data)
    {
        this.data = data;
        this.left = null;
        this.right = null;
    }
}

public class LeafNodesWithValueK {

    // Function to delete leaf Node with value
    // equal to k
    static Node delLeafValueK(Node root, int k)
    {
        if (root == null)
            return null;

        root.left = delLeafValueK(root.left, k);
        root.right = delLeafValueK(root.right, k);

        // If the node is leaf, and its
        // value is equal to k
        if ((root.left == null &&
             root.right == null) &&
             root.data == k)
            return null;

        return root;
    }

    static void postOrder(Node root)
    {
       if (root == null)
          return;
       System.out.print(root.data + " ");
       postOrder(root.left);
       postOrder(root.right);
    }

    // Driver Code
    public static void main(String[] args)
    {
        Node root = new Node(4);
        root.left = new Node(5);
        root.right = new Node(5);
        root.left.left = new Node(3);
        root.left.right = new Node(1);
        root.right.left = new Node(5);

        System.out.println("Nodes in postorder before deletion");
        postOrder(root);
        System.out.println();
        System.out.println("Nodes in post order after required deletion");
        int k = 5;
        delLeafValueK(root, k);
        postOrder(root);
        System.out.println();
    }
}

Python3

# Python program to delete leaf nodes with value equal to k.
class Node:
    def __init__(self, data):
        self.data = data
        self.left = None
        self.right = None

# Function to delete leaf node with value equal to k
def delLeafValueK(root, k):
    if(root == None):
        return None

    root.left = delLeafValueK(root.left, k)
    root.right = delLeafValueK(root.right, k)

    # If the node is leaf, and its value is equal to k
    if((root.left == None and root.right == None) and root.data == k):
        return None

    return root

def postOrder(root):
    if(root == None):
        return
    print(root.data, end=" ")
    postOrder(root.left)
    postOrder(root.right)

if __name__ == "__main__":
    root = Node(4)
    root.left = Node(5)
    root.right = Node(5)
    root.left.left = Node(3)
    root.left.right = Node(1)
    root.right.left = Node(5)

    print("Nodes in postorder before deletion")
    postOrder(root)
    print()
    print("Nodes in post order after required deletion")
    k = 5
    delLeafValueK(root, k)
    postOrder(root)
    print()

# This code is contributed by lokeshmvs21.

C#

// C# program to delete leaf nodes with
// value equal to k.
using System;

public class Node
{
    public int data;
    public Node left;
    public Node right;

    public Node(int data)
    {
        this.data = data;
        this.left = null;
        this.right = null;
    }
}

public class LeafNodesWithValueK
{

    // Function to delete leaf Node with value
    // equal to k
    static Node delLeafValueK(Node root, int k)
    {
        if (root == null)
            return null;

        root.left = delLeafValueK(root.left, k);
        root.right = delLeafValueK(root.right, k);

        // If the node is leaf, and its
        // value is equal to k
        if ((root.left == null &&
            root.right == null) &&
            root.data == k)
            return null;

        return root;
    }

    static void postOrder(Node root)
    {
        if (root == null)
            return;
        Console.Write(root.data + " ");
        postOrder(root.left);
        postOrder(root.right);
    }

    // Driver Code
    public static void Main(String[] args)
    {
        Node root = new Node(4);
        root.left = new Node(5);
        root.right = new Node(5);
        root.left.left = new Node(3);
        root.left.right = new Node(1);
        root.right.left = new Node(5);

        Console.WriteLine("Nodes in postorder before deletion");
        postOrder(root);
        Console.WriteLine();
        Console.WriteLine("Nodes in post order after required deletion");
        int k = 5;
        delLeafValueK(root, k);
        postOrder(root);
        Console.WriteLine();
    }
}

// This code has been contributed by 29AjayKumar

Javascript

<script>

// JavaScript program to delete leaf nodes with
// value equal to k.

class Node
{
    constructor(data)
    {
        this.data = data;
        this.left = null;
        this.right = null;
    }

}

// Function to delete leaf Node with value
// equal to k
function delLeafValueK(root, k)
{
    if (root == null)
        return null;
    root.left = delLeafValueK(root.left, k);
    root.right = delLeafValueK(root.right, k);
    // If the node is leaf, and its
    // value is equal to k
    if ((root.left == null &&
        root.right == null) &&
        root.data == k)
        return null;
    return root;
}
function postOrder(root)
{
    if (root == null)
        return;
    document.write(root.data + " ");
    postOrder(root.left);
    postOrder(root.right);
}

// Driver Code
var root = new Node(4);
root.left = new Node(5);
root.right = new Node(5);
root.left.left = new Node(3);
root.left.right = new Node(1);
root.right.left = new Node(5);
document.write("Nodes in postorder before deletion<br>");
postOrder(root);
document.write("<br>");
document.write("Nodes in post order after required deletion<br>");
var k = 5;
delLeafValueK(root, k);
postOrder(root);
document.write("<br>");

</script>

Output

Nodes in postorder before deletion 
4 5 3 1 5 5 
Nodes in post order after required deletion 
4 5 3 1