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.
Given binary tree [3,9,20,null,null,15,7],
3 / \ 9 20 / \ 15 7
return its depth = 3.
Can solve this question recursively.
- find the max d for the left tree recursively
- find the max d for the right tree recursively
- return the larger d
Below is the white board:
# Definition for a binary tree node. class TreeNode: def __init__(self, x): self.val = x self.left = None self.right = None class Solution: def maxDepth(self, root: TreeNode) -> int: if root is None: return 0 left_d = self.maxDepth(root.left) right_d = self.maxDepth(root.right) return max(left_d, right_d) + 1
- Time complexity is O(n)
Maybe have an iterative solution...