coding test/leetCode

### [leetCode/JS] 222. Count Complete Tree Nodes

쭘봉 2022. 11. 23. 11:07

### 문제 설명

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 `2h` nodes inclusive at the last level `h`.

Design an algorithm that runs in less than `O(n)` time complexity.

### 입출력 예

#### Example 1:

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

Input: root = []
Output: 0

#### Example 3:

Input: root = 
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.

## 내 솔루션

• 어제 DFS, BFS 같은 알고리즘 공부를 해두어서 쉬운 문제였다.
``````var countNodes = function(root) {
let count = 0;
const search = (root) => {
if(!root) return
count++;
search(root.left)
search(root.right)
}

search(root)
return count
};``````

## 감상평

• 복잡하게 count 값을 리턴하는 형태로 할 수 있지만 그럼 귀찮기 때문에 전역으로 처리..