Moderate Trees Question 109 of 224

How do you test whether a binary tree is height-balanced?

DSA interview set · Speak this in 60–90 seconds · Faridabad & Delhi NCR

Train 70%Val 15%Test 15%

Fit on train, tune on val, report on test once.

A bottom-up DFS returns height or a sentinel if any subtree differs by more than one.

Why interviewers care about Trees:

This is a process

question about Trees.

Panels listen for order,

trade-offs, and what you would actually do on a DSA project - not buzzwords.

Stay structured

Name the idea, why it exists, then one short example.

Close cleanly

End with when you use it and one common pitfall.

Before you speak the answer, walk the interviewer through these steps:

1
A bottom-up DFS returns
height or a sentinel if any subtree differs by more than one.
2
You detect imbalance early
without a second height pass.
3
Time is O(n) and
space is O(h).
4
Top-down height calls at
every node would be O(n^2) on skewed trees.
5
Common mistake
What juniors usually get wrong.
6
Close
When you pick this over the alternative.

Here's a short line you can speak, broken into clear beats:

Say this line

“Time is O(n) and space is O(h).”

Break into beats

TimeisOnandspace

Speaking order

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Note: Adapt this scaffold to your own project — keep it under 60–90 seconds.

A bottom-up DFS returns height or a sentinel if any subtree differs by more than one. You detect imbalance early without a second height pass.