[Golang][Leetcode][BinaryTree]刷題系列-222-Count Complete Tree Nodes

Contents
222. Count Complete Tree Nodes
Level : Medium
原題連結 : Click
題目 :
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.
Example :
Note
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
解題思路 :
- 這題Recursive解非常簡潔且易懂~
- 每經過一個node便+1
Recursive解法
- time complexity: O(n) , space complexity: O(1)
Runtime: 12 ms, faster than 99.33% of Go online submissions for Count Complete Tree Nodes.
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