count-complete-tree-nodes

Count Complete Tree Nodes

LeetCode #: 222

Difficulty: Medium

Topic: Binary Search, Tree.

Problem

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 2h nodes inclusive at the last level h.

Example:

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

Output: 6

Solution Explanation

Reference: Concise Java solutions O(log(n)^2) by StefanPochmann