FresherFresher (0–1 yrs)CodingPythonAmazonMicrosoft

Maximum Depth of Binary Tree

Given the root of a binary tree, return its maximum depth (number of nodes along the longest root-to-leaf path).

Answers use simple, clear English.

Time: O(n)Space: O(h)

Quick interview answer

DFS recursively: depth = 1 + max(left, right); null is 0. BFS level-order also works by counting levels.

Detailed answer

DFS recursively: depth = 1 + max(left, right); null is 0. BFS level-order also works by counting levels. Clarify depth vs height terminology if the interviewer uses different words.

Full explanation

Clarify depth vs height terminology if the interviewer uses different words.

Real example & use case

Org-chart depth check to limit nested manager chains in HR software.

Pros & cons

Pros: recursive DFS is tiny. Cons: recursion depth risk on skewed trees — iterative stack/BFS safer.

Code example

class TreeNode:
    def __init__(self, val=0, left=None, right=None):
        self.val, self.left, self.right = val, left, right

def max_depth(root: TreeNode | None) -> int:
    if not root:
        return 0
    return 1 + max(max_depth(root.left), max_depth(root.right))

Practice code · python (view only · no execution)

class TreeNode:
    def __init__(self, val=0, left=None, right=None):
        self.val, self.left, self.right = val, left, right

def max_depth(root: TreeNode | None) -> int:
    if not root:
        return 0
    return 1 + max(max_depth(root.left), max_depth(root.right))

#tree#dfs