If you want to practice data structure and algorithm programs, you can go through data structure and algorithm interview questions.
This is 8th part of java binary tree tutorial.
Java Binary tree tutorial:
- Binary tree in java
- Binary tree preorder traversal
- Binary tree postorder traversal
- Binary tree inorder traversal
- Binary tree level order traversal
- Binary tree spiral order traversal
- Binary tree reverse level order traversal
- Binary tree boundary traversal
- Print leaf nodes of binary tree
- Count leaf nodes in binary tree
- get maximum element in binary tree
- Print all paths from root to leaf in binary tree
- Print vertical sum of binary tree in java
- Get level of node in binary tree in java
- Lowest common ancestor(LCA) in binary tree in java
In this post, we will see about program to count leaf nodes in a binary tree in java
Algorithm-
Steps for counting number of leaf nodes are:
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- If node is null then return 0
- If encountered leaf node(i.e. node.left is null and node.right is null) then return 1.
- Recursively calculate number of leaf nodes using
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Number of leaf nodes= number of leaf nodes in left subtree + number of leaf nodes in right sub tree |
Code for recursion will be:
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// Recursive Solution /* To get the count of leaf nodes in a binary tree*/ public static int getLeafCountOfBinaryTree(TreeNode node) { if(node == null) return 0; if(node.left ==null && node.right==null) return 1; else return getLeafCountOfBinaryTree(node.left)+ getLeafCountOfBinaryTree(node.right); } |
Lets create java program for counting number of leaf nodes:
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package org.arpit.java2blog.binarytree; public class BinaryTreeLeafCount { public static class TreeNode { int data; TreeNode left; TreeNode right; TreeNode(int data) { this.data=data; } } // Recursive Solution /* To get the count of leaf nodes in a binary tree*/ public static int getLeafCountOfBinaryTree(TreeNode node) { if(node == null) return 0; if(node.left ==null && node.right==null) return 1; else return getLeafCountOfBinaryTree(node.left)+ getLeafCountOfBinaryTree(node.right); } public static void main(String[] args) { // Creating a binary tree TreeNode rootNode=createBinaryTree(); System.out.println("Number of leaf nodes in binary tree :"+getLeafCountOfBinaryTree(rootNode)); } public static TreeNode createBinaryTree() { TreeNode rootNode =new TreeNode(40); TreeNode node20=new TreeNode(20); TreeNode node10=new TreeNode(10); TreeNode node30=new TreeNode(30); TreeNode node60=new TreeNode(60); TreeNode node50=new TreeNode(50); TreeNode node70=new TreeNode(70); rootNode.left=node20; rootNode.right=node60; node20.left=node10; node20.right=node30; node60.left=node50; node60.right=node70; return rootNode; } } |
Run above program and you will get following output:
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Number of leaf nodes in binary tree :4 |
Please go through Frequently asked java interview programs for more such programs.
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