Maximum Depth of Binary Tree
Given the root of a binary tree, return its maximum depth.
A binary tree's maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.
Example 1
3
/ \
9 20
/ \
15 7Input
root = [3,9,20,null,null,15,7]Output
3The longest path from the root to a farthest leaf contains 3 nodes.
Example 2
1
\
2Input
root = [1,null,2]Output
2The longest path from the root to the farthest leaf contains 2 nodes.
Constraints
- The number of nodes in the tree is in the range
[0, 10^4]. -100 <= Node.val <= 100