The space complexity was specified as O(1) in the [solution](https://github.com/soapyigu/LeetCode-Swift/blob/master/Tree/MaximumDepthOfBinaryTree.swift), however because of recursion, considering the stack, should it be O(n) instead?
The space complexity was specified as O(1) in the solution, however because of recursion, considering the stack, should it be O(n) instead?