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easyDSA

How do you find the maximum depth of a binary tree?

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01

Understand the problem

Explain computing tree height.

treesrecursion
02

Attempt it yourself

Sketch your approach before reading the solution — that's what interviews test.

Nudge consolestandby

Stuck? Beam a request up — the console returns a conceptual nudge that guides your logic without spoiling the implementation.

03

Study the solution

Recurse: depth of a node = 1 + max(depth(left), depth(right)), with null nodes contributing 0. It visits each node once — O(n) time, O(h) stack space. A BFS level count gives the same answer iteratively.

Solution ready — 2 min read

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04

Read the code

Recursive height
Run Playground
class TreeNode:
    def __init__(self, val, left=None, right=None):
        self.val, self.left, self.right = val, left, right

def max_depth(root):
    if not root:
        return 0
    return 1 + max(max_depth(root.left), max_depth(root.right))


# --- demo ---  tree of depth 3
root = TreeNode(3, TreeNode(9), TreeNode(20, TreeNode(15), TreeNode(7)))
print(max_depth(root))   # 3
05

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