Solution (leetcode-in-java 1.21 API)

java.lang.Object
- g0201_0300.s0222_count_complete_tree_nodes.Solution

```
public class Solution
extends Object
```
222 - Count Complete Tree Nodes.
Medium

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.

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 * 10⁴].
- 0 <= Node.val <= 5 * 10⁴
- The tree is guaranteed to be complete.

- Constructor Summary
  
  Constructors
  Constructor Description
  
  Solution()
- Method Summary
  
  All Methods Instance Methods Concrete Methods
  Modifier and Type Method Description
  
  int countNodes(TreeNode root)
  - Methods inherited from class java.lang.Object
    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail
- Solution
```
public Solution()
```

Method Detail

countNodes

public int countNodes(TreeNode root)