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Delete leaf nodes with value as x
  • Difficulty Level : Medium
  • Last Updated : 02 Nov, 2020

Given a binary tree and a target integer x, delete all the leaf nodes having value as x. Also, delete the newly formed leaves with the target value as x.

Example:

Input : x = 5  
            6
         /     \
        5       4
      /   \       \
     1     2       5 
Output : 
            6
         /     \
        5       4
      /   \  
     1     2 
Inorder Traversal is 1 5 2 6 4

Source: Microsoft Interview

We traverse the tree in postorder fashion and recursively delete the nodes. The approach is very similar to this and this problem.

C++




// CPP code to delete all leaves with given
// value.
#include <bits/stdc++.h>
using namespace std;
  
// A binary tree node
struct Node {
    int data;
    struct Node *left, *right;
};
  
// A utility function to allocate a new node
struct Node* newNode(int data)
{
    struct Node* newNode = new Node;
    newNode->data = data;
    newNode->left = newNode->right = NULL;
    return (newNode);
}
  
Node* deleteLeaves(Node* root, int x)
{
    if (root == NULL)
        return nullptr;
    root->left = deleteLeaves(root->left, x);
    root->right = deleteLeaves(root->right, x);
  
    if (root->data == x && root->left == NULL && 
                          root->right == NULL) {
         
        return nullptr;
    }
    return root;
}
  
void inorder(Node* root)
{
    if (root == NULL)
        return;
    inorder(root->left);
    cout << root->data << " ";
    inorder(root->right);
}
  
// Driver program
int main(void)
{
    struct Node* root = newNode(10);
    root->left = newNode(3);
    root->right = newNode(10);
    root->left->left = newNode(3);
    root->left->right = newNode(1);
    root->right->right = newNode(3);
    root->right->right->left = newNode(3);
    root->right->right->right = newNode(3);
    deleteLeaves(root, 3);
    cout << "Inorder traversal after deletion : ";
    inorder(root);
    return 0;
}

Java




// Java code to delete all leaves with given 
// value. 
class GfG { 
  
// A binary tree node 
static class Node { 
    int data; 
    Node left, right; 
}
  
// A utility function to allocate a new node 
static Node newNode(int data) 
    Node newNode = new Node(); 
    newNode.data = data; 
    newNode.left = null;
    newNode.right = null
    return (newNode); 
  
static Node deleteLeaves(Node root, int x) 
    if (root == null
        return null
    root.left = deleteLeaves(root.left, x); 
    root.right = deleteLeaves(root.right, x); 
  
    if (root.data == x && root.left == null && root.right == null) { 
  
        return null
    
    return root; 
  
static void inorder(Node root) 
    if (root == null
        return
    inorder(root.left); 
    System.out.print(root.data + " "); 
    inorder(root.right); 
  
// Driver program 
public static void main(String[] args) 
    Node root = newNode(10); 
    root.left = newNode(3); 
    root.right = newNode(10); 
    root.left.left = newNode(3); 
    root.left.right = newNode(1); 
    root.right.right = newNode(3); 
    root.right.right.left = newNode(3); 
    root.right.right.right = newNode(3); 
    deleteLeaves(root, 3); 
    System.out.print("Inorder traversal after deletion : "); 
    inorder(root); 
}

Python3




# Python3 code to delete all leaves 
# with given value. 
  
# A utility class to allocate a new node 
class newNode:
    def __init__(self, data):
        self.data = data 
        self.left = self.right = None
  
def deleteLeaves(root, x):
    if (root == None):
        return None
    root.left = deleteLeaves(root.left, x) 
    root.right = deleteLeaves(root.right, x) 
  
    if (root.data == x and 
        root.left == None and 
        root.right == None):
        return None
    return root
  
def inorder(root):
    if (root == None): 
        return
    inorder(root.left) 
    print(root.data, end = " "
    inorder(root.right)
  
# Driver Code
if __name__ == '__main__'
    root = newNode(10
    root.left = newNode(3
    root.right = newNode(10
    root.left.left = newNode(3
    root.left.right = newNode(1
    root.right.right = newNode(3
    root.right.right.left = newNode(3
    root.right.right.right = newNode(3
    deleteLeaves(root, 3
    print("Inorder traversal after deletion : "
    inorder(root)
  
# This code is contributed by PranchalK

C#




// C# code to delete all leaves with given 
// value.
using System;
      
class GfG 
  
    // A binary tree node 
    class Node 
    
        public int data; 
        public Node left, right; 
    }
  
    // A utility function to allocate a new node 
    static Node newNode(int data) 
    
        Node newNode = new Node(); 
        newNode.data = data; 
        newNode.left = null;
        newNode.right = null
        return (newNode); 
    
  
    static Node deleteLeaves(Node root, int x) 
    
        if (root == null
            return null
        root.left = deleteLeaves(root.left, x); 
        root.right = deleteLeaves(root.right, x); 
  
        if (root.data == x && 
            root.left == null && 
            root.right == null
        
  
            return null
        
        return root; 
    
  
    static void inorder(Node root) 
    
        if (root == null
            return
        inorder(root.left); 
        Console.Write(root.data + " "); 
        inorder(root.right); 
    
  
    // Driver code 
    public static void Main(String[] args) 
    
        Node root = newNode(10); 
        root.left = newNode(3); 
        root.right = newNode(10); 
        root.left.left = newNode(3); 
        root.left.right = newNode(1); 
        root.right.right = newNode(3); 
        root.right.right.left = newNode(3); 
        root.right.right.right = newNode(3); 
        deleteLeaves(root, 3); 
        Console.Write("Inorder traversal after deletion : "); 
        inorder(root); 
    }
}
  
// This code is contributed by PrinciRaj1992


Output:
Inorder traversal after deletion : 3 1 10 10

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