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Sum of all leaf nodes of binary tree

Given a binary tree, find the sum of all the leaf nodes.

Examples:

Input : 
        1
      /   
     2     3
    /    / 
   4   5 6   7
          
           8
Output :
Sum = 4 + 5 + 8 + 7 = 24



The idea is to traverse the tree in any fashion and check if the node is the leaf node or not. If the node is the leaf node, add node data to sum variable.

Following is the implementation of above approach.

C++

// CPP program to find sum of
// all leaf nodes of binary tree
#include<bits/stdc++.h>
using namespace std;
  
// struct binary tree node
struct Node{
    int data;
    Node *left, *right;
};
  
// return new node 
Node *newNode(int data){
    Node *temp = new Node();
    temp->data = data;
    temp->left = temp->right = NULL;
}
  
// utility function which calculates
// sum of all leaf nodes
void leafSum(Node *root, int *sum){
    if (!root)
        return;
  
    // add root data to sum if 
    // root is a leaf node
    if (!root->left && !root->right)
        *sum += root->data;
  
    // propagate recursively in left
    // and right subtree
    leafSum(root->left, sum);
    leafSum(root->right, sum);
}
  
// driver program
int main(){
      
    //contruct binary tree
    Node *root = newNode(1);
    root->left = newNode(2);
    root->left->left = newNode(4);
    root->left->right = newNode(5);
    root->right = newNode(3);
    root->right->right = newNode(7);
    root->right->left = newNode(6);
    root->right->left->right = newNode(8);
      
    // variable to store sum of leaf nodes
    int sum = 0;
    leafSum(root, &sum);
    cout << sum << endl;
    return 0;
}

Java

// Java program to find sum of
// all leaf nodes of binary tree
public class GFG {
   
    // user define class node
    static class Node{
        int data;
        Node left, right;
          
        // constructor
        Node(int data){
            this.data = data;
            left = null;
            right = null;
        }
    }
      
    static int sum;
      
    // utility function which calculates
    // sum of all leaf nodes
    static void leafSum(Node root){
        if (root == null)
            return;
       
        // add root data to sum if 
        // root is a leaf node
        if (root.left == null && root.right == null)
            sum += root.data;
       
        // propagate recursively in left
        // and right subtree
        leafSum(root.left);
        leafSum(root.right);
    }
       
    // driver program
    public static void main(String args[])
    {
        //contruct binary tree
        Node root = new Node(1);
        root.left = new Node(2);
        root.left.left = new Node(4);
        root.left.right = new Node(5);
        root.right = new Node(3);
        root.right.right = new Node(7);
        root.right.left = new Node(6);
        root.right.left.right = new Node(8);
           
        // variable to store sum of leaf nodes
        sum = 0;
        leafSum(root);
        System.out.println(sum);
    }
}
// This code is contributed by Sumit Ghosh

Python3

# Python3 Program to find the 
#sum of leaf nodes of a binary tree
  
  
 # Class for node creation
class Node:
      
     # Constructor
    def __init__(self, data):             
        self.data = data
        self.left = None
        self.right = None
  
# Utility function to calculate 
# the sum of all leaf nodes
def leafSum(root):
    global total
    if root is None:
        return
    if (root.left is None and root.right is None):
        total += root.data
    leafSum(root.left)
    leafSum(root.right)
  
# Binary tree Fromation
if __name__=='__main__':
    root = Node(1)
    root.left = Node(2)
    root.left.left = Node(4)
    root.left.right = Node(5)
    root.right = Node(3)
    root.right.right = Node(7)
    root.right.left = Node(6)
    root.right.left.right = Node(8)
# Variable to store the sum of leaf nodes
    total = 0
    leafSum(root)
# Printing the calculated sum
    print(total)
  
# This code is contributed by Naren Sai Krishna

C#

using System;
  
// C# program to find sum of 
// all leaf nodes of binary tree 
public class GFG
{
  
    // user define class node 
    public class Node
    {
        public int data;
        public Node left, right;
  
        // constructor 
        public Node(int data)
        {
            this.data = data;
            left = null;
            right = null;
        }
    }
  
    public static int sum;
  
    // utility function which calculates 
    // sum of all leaf nodes 
    public static void leafSum(Node root)
    {
        if (root == null)
        {
            return;
        }
  
        // add root data to sum if  
        // root is a leaf node 
        if (root.left == null && root.right == null)
        {
            sum += root.data;
        }
  
        // propagate recursively in left 
        // and right subtree 
        leafSum(root.left);
        leafSum(root.right);
    }
  
    // driver program 
    public static void Main(string[] args)
    {
        //contruct binary tree 
        Node root = new Node(1);
        root.left = new Node(2);
        root.left.left = new Node(4);
        root.left.right = new Node(5);
        root.right = new Node(3);
        root.right.right = new Node(7);
        root.right.left = new Node(6);
        root.right.left.right = new Node(8);
  
        // variable to store sum of leaf nodes 
        sum = 0;
        leafSum(root);
        Console.WriteLine(sum);
    }
}
  
  // This code is contributed by Shrikant13


Output:

24

Time Complexity : O(n)

Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.



This article is attributed to GeeksforGeeks.org

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