104. Maximum Depth of Binary Tree

Given a binary tree, find its maximum depth.

The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.

Note: A leaf is a node with no children.

Example:

Given binary tree [3,9,20,null,null,15,7],

return its depth = 3.

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Intuition
F(node) = 1 + Max( F(node.left), F(node.right))
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Time - O(n)
Space - O(h) - recursive call stack
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Related problems
111-minimum-depth-of-binary-tree
366-find-leaves-of-binary-tree
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	/**
	* Definition for a binary tree node.
	* public class TreeNode {
	* int val;
	* TreeNode left;
	* TreeNode right;
	* TreeNode(int x) { val = x; }
	* }
	*/
	class Solution {
	public int maxDepth(TreeNode root) {
	if (root == null) {
	return 0;
	}
	int lDepth = maxDepth(root.left);
	int rDepth = maxDepth(root.right);

	return 1 + Math.max(lDepth, rDepth);
	}
	}

	# Definition for a binary tree node.
	# class TreeNode:
	# def __init__(self, val=0, left=None, right=None):
	# self.val = val
	# self.left = left
	# self.right = right
	class Solution:
	def maxDepth(self, root: Optional[TreeNode]) -> int:
	if not root:
	return 0

	return 1 + max(self.maxDepth(root.left), self.maxDepth(root.right))

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