C Program to Find the Product of All Leaf Nodes in a Binary Tree

In a Binary Tree, a leaf node is a node that does not have a left or right child. This program will calculate the product of all leaf nodes using recursion.

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📝 Problem Statement

B) Write a C Program to find the product of all leaf nodes of a binary tree.

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💡 Logic (Student-Friendly Steps)

1. Define a structure for a binary tree node with:
   • data
   • left pointer
   • right pointer
2. Create the binary tree nodes (manually or using insertion logic).
3. Write a recursive function productOfLeaves:
   • If node is NULL, return 1 (neutral element for multiplication).
   • If node is a leaf (both left and right are NULL), return its value.
   • Otherwise, return the product of left and right subtrees.
4. Call the function from main() and print the result.

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💻 Source Code (Student-Friendly)

#include <stdio.h>
#include <stdlib.h>

// Node structure
struct node
{
    int data;
    struct node *left;
    struct node *right;
};

// Function to create a new node
struct node* createNode(int value)
{
    struct node* newnode = (struct node*)malloc(sizeof(struct node));
    newnode->data = value;
    newnode->left = NULL;
    newnode->right = NULL;
    return newnode;
}

// Recursive function to find product of leaf nodes
int productOfLeaves(struct node* root)
{
    if(root == NULL)
        return 1;

    if(root->left == NULL && root->right == NULL)
        return root->data;

    return productOfLeaves(root->left) * productOfLeaves(root->right);
}

int main()
{
    struct node* root = NULL;

    // Manually creating binary tree for simplicity
    // Example tree:
    //        2
    //       / \
    //      3   5
    //     / \
    //    4   6
    root = createNode(2);
    root->left = createNode(3);
    root->right = createNode(5);
    root->left->left = createNode(4);
    root->left->right = createNode(6);

    int product = productOfLeaves(root);
    printf("Product of leaf nodes: %d\n", product);

    return 0;
}

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🖥️ Sample Output

Product of leaf nodes: 120

Explanation: Leaf nodes are 4, 6, and 5. Product = 4 × 6 × 5 = 120

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🎓 Viva Questions with Answers

1. What is a leaf node?

A node with no left or right child.

2. Why do we return 1 for NULL nodes?

1 is the neutral element for multiplication, so it doesn’t affect the product.

3. How do we check if a node is a leaf?

If node->left == NULL && node->right == NULL.

4. What traversal is used here?

Preorder traversal logic is used recursively.

5. What is the time complexity of this program?

O(n), because each node is visited once.