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🏏 The 18-Day DSA Cover Drive | Day 4: The 5 Questions I Ask Before Solving Any DSA Problem

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🏏 The 18-Day DSA Cover Drive | Day 4— How I Identify DSA Patterns Before Writing Code

Learn DSA one pattern at a time.

What's up, DEV Community! 👋

Welcome back to The 18-Day DSA Cover Drive.

🏆 Kohli Corner

🏏 "The best batters don't guess the ball. They read it."

Virat Kohli doesn't decide his shot before the bowler releases the ball.

He watches.

He reads.

Then he chooses the perfect shot.

💡 DSA is no different.

Don't memorize solutions.

Read the problem first. Choose the right pattern. Then write the code.

🧩 Day 4 — Pattern Recognition

When I started learning DSA, every problem looked different.

Some people said,

"Just solve 500 questions."

But I realized something...

Experienced programmers don't memorize problems.

They recognize patterns.

Now, before writing a single line of code, I ask myself these 5 simple questions.

❓ Question 1

Is the data continuous?

Look for words like:

  • Subarray
  • Substring
  • Contiguous
  • Continuous

🎯 Think: Sliding Window

❓ Question 2

Does the order matter?

If YES

➡️ Keep the original order.

If NO

➡️ Sorting might make the problem much easier.

❓ Question 3

Am I searching for the same thing repeatedly?

Look for words like:

  • Frequency
  • Count
  • Duplicate
  • Lookup
  • Pair
  • Already seen
  • Mapping

🎯 Think: Dictionary (HashMap)

Ask yourself:

"Do I need to remember information?"

If yes...

Use a Dictionary.

❓ Question 4

Am I comparing from both ends?

Keywords:

  • Sorted Array
  • Palindrome
  • Reverse
  • Pair
  • Left
  • Right

🎯 Think: Two Pointers

❓ Question 5

Is my brute-force solution repeating work?

If you're calculating the same thing again...

There is probably a better approach.

Ask yourself:

"Can I reuse my previous work?"

⚡ My Pattern Decision Tree 

Problem
   │
   ▼
Subarray / Substring?
   │
 YES ─────────► Sliding Window
   │
   NO
   │
Need Frequency?
   │
 YES ─────────► Dictionary
   │
   NO
   │
Need Unique Elements?
   │
 YES ─────────► Set
   │
   NO
   │
Sorted / Palindrome / Pair?
   │
 YES ─────────► Two Pointers
   │
   NO
   │
Start with Brute Force.
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🏏 Cover Drive Cheat Sheet

If the problem says... Think... Ask Yourself
Frequency, Count, Lookup 🗂️ Dictionary Do I need to remember information?
Duplicate, Unique, Visited 📦 Set Do I only care if it exists?
Sorted Array, Pair, Reverse, Palindrome 👉👈 Two Pointers Can two indices move together?
Subarray, Substring, Contiguous 🪟 Sliding Window Can I reuse previous work?
Window Size = K 📏 Fixed Sliding Window Remove one, add one?
Longest / Shortest 🔄 Variable Sliding Window Expand or shrink the window?

💼 Interview Insight

One habit I'm trying to build:

❌ Don't jump into coding.

✅ Spend the first minute asking:

  • What are the keywords?
  • Which pattern fits?
  • Why does it fit?

Choosing the correct pattern is often harder than writing the code.

🏏 Nets Practice

Which pattern would you choose?

🥎 Problem 1

Find the longest substring without repeating characters.

🤔 Pattern?

🥎 Problem 2

Find whether an array contains duplicate elements.

🤔 Pattern?

🥎 Problem 3

Find two numbers in a sorted array whose sum equals the target.

🤔 Pattern?

🥎 Problem 4

Find the maximum sum of a subarray of size k.

🤔 Pattern?

👇 Comment only the pattern names.

No code.

Let's see how many you get right!

🏏 Cover Drive of the Day

🏏 Concept: Pattern Recognition

⭐ Goal: Identify the pattern before writing code.

💼 Interview Insight: One minute of thinking can save thirty minutes of debugging.

💬 Let's Discuss

When you first started DSA...

Which pattern confused you the most?

Or...

Do you have another trick for identifying patterns quickly?

I'd love to learn from your experience too! 👇

18DayDSACoverDrive | Python | DSA | Algorithms | Beginners

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