CS101-LC01 — What is LeetCode? (Why Everyone Uses It)
~30 minutes
🎯 Why This Chapter Matters
Before solving problems, you must understand why you are solving them.
LeetCode is not just a website.
It is a thinking framework used worldwide to evaluate engineers.
🤔 What is LeetCode?
LeetCode is an online platform for practicing:
- Algorithms
- Data Structures
- Logical problem solving
- Interview-style coding questions
Problems range from:
- Beginner (arrays, loops)
- Intermediate (hash maps, trees)
- Advanced (DP, graphs, system thinking)
🌍 Who Uses LeetCode?
LeetCode-style questions are used by:
- Meta (Facebook)
- Amazon
- Microsoft
- Apple
- Netflix
- Startups & research labs
Even if the interview is not on LeetCode,
the problem patterns are the same.
🧠 What LeetCode Is REALLY Training
LeetCode is NOT about memorizing code.
It trains you to:
- Break big problems into smaller ones
- Recognize patterns
- Choose the right data structure
- Optimize time & memory
- Explain your reasoning clearly
🔍 What Interviewers Look For
Interviewers are evaluating how you think, not just the final answer.
They care about:
- Clear understanding of the problem
- Logical step-by-step reasoning
- Clean, readable code
- Correct time complexity (Big-O)
- Ability to improve a slow solution
🧪 Interview Reality Check
You are usually expected to:
- Explain the problem in your own words
- Start with a simple (even slow) solution
- Analyze time complexity
- Improve it
- Communicate clearly
Perfect code ≠ Perfect interview
Clear thinking = Pass
🧠 Common Beginner Misunderstanding
Does LeetCode measure intelligence?
❌ No
✅ It measures problem-solving patterns
Someone who practiced patterns will outperform
someone who is “smart but untrained”.
This is learnable, not talent-based.
🧩 Examples of Patterns You Will Learn
| Pattern | Example |
|---|---|
| Two pointers | Palindrome check |
| Hash map | Two Sum |
| Sliding window | Subarray problems |
| Prefix sum | Range queries |
| Stack | Valid parentheses |
| BFS / DFS | Tree & graph traversal |
Once you see the pattern,
many problems feel similar.
🏫 Why LeetCode is Used in Exams
LeetCode-style questions test:
- Logic
- Edge cases
- Complexity awareness
- Coding discipline
These skills apply to:
- Midterm / final exams
- Programming contests
- Research code
- Real-world software
🏁 How to Use LeetCode Correctly
❌ Wrong way:
- Copy solution
- Memorize code
- Skip explanation
✅ Right way:
- Understand the idea
- Rewrite in your own style
- Analyze complexity
- Explain out loud
If you can teach it, you truly understand it.
🎯 Goal of This Course
By the end of this course, you should be able to:
- Look at a problem
- Identify its pattern
- Choose the right approach
- Write clean, efficient code
- Explain your solution confidently
That is exactly what interviewers want.
🚀 Final Message
LeetCode is not a test of intelligence.
It is training for structured thinking.
If you practice correctly,
you will think like a software engineer.
And that skill lasts a lifetime 💡