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Delete leaf nodes with value k
  • Difficulty Level : Medium
  • Last Updated : 07 Aug, 2020

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. 

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();
    }
}

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

 

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