Program to count leaf nodes in a binary tree - GeeksforGeeks

10 Jan, 2022
A node is a leaf node if both left and right child nodes of it are NULL. Here is an algorithm to get the leaf node count.
getLeafCount(node)
1) If node is NULL then return 0.
2) Else If left and right child nodes are NULL return 1.
3) Else recursively calculate leaf count of the tree using below formula.
    Leaf count of a tree = Leaf count of left subtree + 
                                 Leaf count of right subtree
Leaf count for the above tree is 3.
Implementation:  
C++
C
Java
Python3
C#
Javascript
// C++ implementation to find leaf// count of a given Binary tree#include <bits/stdc++.h>using namespace std; /* A binary tree node has data,pointer to left child anda pointer to right child */struct node{    int data;    struct node* left;    struct node* right;}; /* Function to get the countof leaf nodes in a binary tree*/unsigned int getLeafCount(struct node* node){    if(node == NULL)            return 0;    if(node->left == NULL && node->right == NULL)        return 1;            else        return getLeafCount(node->left)+            getLeafCount(node->right);} /* Helper function that allocates a new node with thegiven data and NULL left and right pointers. */struct node* newNode(int data){    struct node* node = (struct node*)                    malloc(sizeof(struct node));    node->data = data;    node->left = NULL;    node->right = NULL;     return(node);} /*Driver code*/int main(){    /*create a tree*/    struct node *root = newNode(1);    root->left = newNode(2);    root->right = newNode(3);    root->left->left = newNode(4);    root->left->right = newNode(5);     /*get leaf count of the above created tree*/cout << "Leaf count of the tree is : "<<                getLeafCount(root) << endl;return 0;} // This code is contributed by SHUBHAMSINGH10
// C implementation to find leaf count of a given Binary tree#include <stdio.h>#include <stdlib.h> /* A binary tree node has data, pointer to left child   and a pointer to right child */struct node{    int data;    struct node* left;    struct node* right;}; /* Function to get the count of leaf nodes in a binary tree*/unsigned int getLeafCount(struct node* node){  if(node == NULL)          return 0;  if(node->left == NULL && node->right==NULL)         return 1;             else    return getLeafCount(node->left)+           getLeafCount(node->right);     } /* Helper function that allocates a new node with the   given data and NULL left and right pointers. */struct node* newNode(int data){  struct node* node = (struct node*)                       malloc(sizeof(struct node));  node->data = data;  node->left = NULL;  node->right = NULL;     return(node);} /*Driver program to test above functions*/ int main(){  /*create a tree*/   struct node *root = newNode(1);  root->left        = newNode(2);  root->right       = newNode(3);  root->left->left  = newNode(4);  root->left->right = newNode(5);        /*get leaf count of the above created tree*/  printf("Leaf count of the tree is %d", getLeafCount(root));     getchar();  return 0;}
// Java implementation to find leaf count of a given Binary tree  /* Class containing left and right child of current node and key value*/class Node{    int data;    Node left, right;      public Node(int item)    {        data = item;        left = right = null;    }}  public class BinaryTree{    //Root of the Binary Tree    Node root;          /* Function to get the count of leaf nodes in a binary tree*/    int getLeafCount()    {        return getLeafCount(root);    }      int getLeafCount(Node node)    {        if (node == null)            return 0;        if (node.left == null && node.right == null)            return 1;        else            return getLeafCount(node.left) + getLeafCount(node.right);    }      /* Driver program to test above functions */    public static void main(String args[])    {        /* create a tree */        BinaryTree tree = new BinaryTree();        tree.root = new Node(1);        tree.root.left = new Node(2);        tree.root.right = new Node(3);        tree.root.left.left = new Node(4);        tree.root.left.right = new Node(5);                  /* get leaf count of the above tree */        System.out.println("The leaf count of binary tree is : "                             + tree.getLeafCount());    }} // This code has been contributed by Mayank Jaiswal(mayank_24)
# Python program to count leaf nodes in Binary Tree # A Binary tree nodeclass Node:         # Constructor to create a new node    def __init__(self, data):        self.data = data        self.left = None        self.right = None # Function to get the count of leaf nodes in binary treedef getLeafCount(node):    if node is None:        return 0    if(node.left is None and node.right is None):        return 1    else:        return getLeafCount(node.left) + getLeafCount(node.right)  # Driver program to test above functionroot = Node(1)root.left = Node(2)root.right = Node(3)root.left.left = Node(4)root.left.right = Node(5) print ("Leaf count of the tree is %d" %(getLeafCount(root))) #This code is contributed by Nikhil Kumar Singh(nickzuck_007)
using System; // C# implementation to find leaf count of a given Binary tree /* Class containing left and right child of current  node and key value*/public class Node{    public int data;    public Node left, right;     public Node(int item)    {        data = item;        left = right = null;    }} public class BinaryTree{    //Root of the Binary Tree    public Node root;     /* Function to get the count of leaf nodes in a binary tree*/    public virtual int LeafCount    {        get        {            return getLeafCount(root);        }    }     public virtual int getLeafCount(Node node)    {        if (node == null)        {            return 0;        }        if (node.left == null && node.right == null)        {            return 1;        }        else        {            return getLeafCount(node.left) + getLeafCount(node.right);        }    }     /* Driver program to test above functions */    public static void Main(string[] args)    {        /* create a tree */        BinaryTree tree = new BinaryTree();        tree.root = new Node(1);        tree.root.left = new Node(2);        tree.root.right = new Node(3);        tree.root.left.left = new Node(4);        tree.root.left.right = new Node(5);         /* get leaf count of the above tree */        Console.WriteLine("The leaf count of binary tree is : " + tree.LeafCount);    }}   // This code is contributed by Shrikant13
<script>    // Javascript implementation to find leaf count of a given Binary tree         /* A binary tree node has data,    pointer to left child and    a pointer to right child */    class node    {        constructor(data) {           this.left = null;           this.right = null;           this.data = data;        }    }         /* Function to get the count    of leaf nodes in a binary tree*/    function getLeafCount(node)    {        if(node == null)                return 0;        if(node.left == null && node.right == null)            return 1;                else            return getLeafCount(node.left)+                getLeafCount(node.right);    }     /* Helper function that allocates a new node with the    given data and NULL left and right pointers. */    function newNode(data)    {        let Node = new node(data);        return(Node);    }         /*create a tree*/    let root = newNode(1);    root.left = newNode(2);    root.right = newNode(3);    root.left.left = newNode(4);    root.left.right = newNode(5);           /*get leaf count of the above created tree*/    document.write("The leaf count of binary tree is : " + getLeafCount(root));         // This code is contributed by mukesh07.</script>
Output: 
The leaf count of binary tree is : 3
Time & Space Complexities: Since this program is similar to traversal of tree, time and space complexities will be same as Tree traversal (Please see our Tree Traversal post for details) 
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Please write comments if you find any bug in the above programs/algorithms or other ways to solve the same problem.  
shrikanth13
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mukesh07
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