What is the Overview (Monotonic Stack) pattern?

The Overview (Monotonic Stack) is a common coding interview pattern in Stack problems. It provides a structured approach to solving related algorithm challenges efficiently.

When should I use Overview (Monotonic Stack)?

Use the Overview (Monotonic Stack) pattern when you encounter problems matching its characteristics. Check the "When to Use" and "Clues" sections in the lesson for specific indicators.

Is Overview (Monotonic Stack) asked in FAANG interviews?

Yes, Overview (Monotonic Stack) is an essential pattern commonly tested in FAANG and top tech company technical interviews.

Stack

Medium

Overview (Monotonic Stack)

Understand the Monotonic Stack pattern for finding Next Greater/Smaller Elements.

10 min

What is a Monotonic Stack?

A Monotonic Stack is a stack where elements are always sorted (either increasing or decreasing). It allows us to solve problems related to Next Greater Element or Next Smaller Element in O(N) time.

Monotonic Increasing: [1, 2, 5, 8]. Used to find the Next Smaller Element.
Monotonic Decreasing: [10, 8, 4, 1]. Used to find the Next Greater Element.

How It Works

We iterate through an array. Before pushing a new element X, we Pop all elements from the stack that violate the monotonic property.

Example (Next Greater Element):
We want a Decreasing Stack. If current X > Stack.Top, it means X is the "Next Greater Element" for Stack.Bottom. We pop until X < Stack.Top, then push X.

Interactive Visualization

Step 1 / 1

Empty Stack

Top Index: -1

Initializing...

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