Find the Size of the Binary Tree

Objective: Given a Binary tree, Find the size of the tree.

Note : Size of the tree is number of nodes in the tree

Input: A Binary Tree.

Output: Size of the tree.

Example :


Approach :

  • Very Simple solution
  • Start from the root.
  • Size = 1 (for the root) + Size Of left Sub-Tree + Size Of right Sub-Tree
  • solve the left sub-tree and right sub-tree recursively.

Time Complexity : O(n)


public class SizeofTree {
public int getSize(Node root){
return 0;
return 1 + getSize(root.left) + getSize(root.right);
public static void main(String args[]){
Node root = new Node(5);
root.left = new Node(15);
root.right = new Node(25);
root.left.left = new Node(20);
root.left.right = new Node(30);
root.right.left = new Node(2);
root.right.right = new Node(10);
SizeofTree t = new SizeofTree();
System.out.println("Size of the Tree is : " + t.getSize(root));
class Node{
int data;
Node left;
Node right;
public Node(int data){ = data;
this.left = null;
this.right = null;

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Size of the Tree is : 7

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