High Stack Question 154 of 224

How do you find the largest rectangle of 1s in a histogram of bar heights?

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

StackLIFOlast in, first out

QueueFIFOfirst in, first out

Monotonic increasing stack of indices

Why interviewers care about Stack:

This is a process

question about Stack.

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
Define it
Monotonic increasing stack of indices
2
when a lower bar
arrives, pop and compute height * width using the new top as the left bound.
3
Send a 0-height sentinel
at the end.
4
Time is O(n) and
space is O(n).
5
Common mistake
Brute min-over-range is O(n^2).
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(n).”

Break into beats

TimeisOnandspace

Speaking order

2987408337471632900

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

Monotonic increasing stack of indices when a lower bar arrives, pop and compute height * width using the new top as the left bound.