Count Complete Tree Nodes

Given a complete binary tree, count the number of nodes.

Note:

Definition of a complete binary tree from Wikipedia:
In a complete binary tree every level, except possibly the last, is completely filled, and all nodes in the last level are as far left as possible. It can have between 1 and 2^h nodes inclusive at the last level h.

Example:

Input: 
    1
   / \
  2   3
 / \  /
4  5 6

Output: 6

 /**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class Solution {
    public int countNodes(TreeNode root) {
        if(root == null){
        return 0;
    }
 
    return 1 + countNodes(root.left) + countNodes(root.right);
    }
}

Try it on Leetcode

Here, we are going to solve it recursively.

If root is null return 0.

Else Recursively count left nodes and right nodes and at each time 1 is added.

Finally return the result.

Related Posts:

Click here for May month challenges with solution and explanation
Click here for April month challenges with solution and explanation

Click here for June Month challenges with solution and explanation

Click Follow button to receive updates from us instantly.

Please let us know about your views in comment section.

                                                     😍..Happy Coding...😍