#222
Count Complete Tree Nodes
newbie · 260 · lc easy +19 · verified · 72.1% accepted · 9,456 likes · top 81%
Description
Count the nodes in the complete binary tree rooted at root.
A complete binary tree fills every level except possibly the last, where nodes are packed as far left as possible; the last level holds between 1 and 2h nodes at height h.
Aim for an algorithm faster than O(n).
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
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