Skip to content

Practice Count Complete Tree Nodes

Read the task, work through the examples, and check your approach against the constraints. Use the original LeetCode task for coding and submissions.

Easy#222
LeetCode Problem

Count Complete Tree Nodes

Binary SearchBit ManipulationTreeBinary Tree

Problem Statement

Given the root of a complete binary tree, return the number of the nodes in the tree. According to Wikipedia, every level, except possibly the last, is completely filled in a complete binary tree, 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. Design an algorithm that runs in less than O(n) time complexity.

Source: Count Complete Tree Nodes on LeetCode. Use the original task for its coding environment and submissions.

Examples

# Example 1

Input
root = [1,2,3,4,5,6]
Output
6

# Example 2

Input
root = []
Output
0

# Example 3

Input
root = [1]
Output
1

Constraints

The number of nodes in the tree is in the range [0, 5 * 10^4].
0 <= Node.val <= 5 * 10^4
The tree is guaranteed to be complete.

Related LeetCode Problems

Practice more problems similar to Count Complete Tree Nodes.

94 Binary Tree Inorder Traversal Easy95 Unique Binary Search Trees II Medium96 Unique Binary Search Trees Medium98 Validate Binary Search Tree Medium99 Recover Binary Search Tree Medium
← Previous Maximal SquareNext → Rectangle Area

Review your practice with PhantomCodeAI

After trying the problem yourself, use the app to discuss your approach, complexity, and edge cases.

Start Free