What LeetCode is and why it matters
If you've tried studying LeetCode before and felt lost — "why do I even need to know this?" — this lesson is for you. Before any technique, let's understand the game we're learning to play.
What LeetCode is
LeetCode is a website with thousands of programming problems: a prompt describes a task (e.g. "find two numbers that add up to X"), you write a function that solves it, and the site runs your function against dozens of automatic test cases. Green = passed all of them; red = failed one.
But the goal is never "solve all 3000 problems." It's something else.
Why people study this
Two reasons, and both matter to you:
- Technical interviews. Almost every tech company — from the giants to startups — uses problems in this style to interview. Being able to solve them is, in practice, what unlocks many job offers.
- Algorithmic reasoning. Solving these problems trains you to see structure in a messy problem and to turn "slow brute force" into "an elegant, fast solution." That skill is valuable for programming as a whole, not just for the interview.
Why you may have gotten stuck before
The most common mistake (and the reason so many people give up) is studying like this:
❌ Read a problem's solution → "ah, got it" → next problem → when it's time to solve it on your own, complete blank.
This fails because you're memorizing solutions, not learning to think. Each problem feels unique and new. It's like trying to learn to cook by memorizing 3000 recipes, one by one.
The key shift: the problems repeat in patterns. Beneath prompts that look completely different lives the same half dozen ideas. "Find two numbers that add up to X", "find the substring with no repeats", "detect a cycle in a list" — they seem like distinct topics, but each is an application of a pattern you can learn once and reuse forever.
Learning ~20 patterns gives you the tools to attack thousands of problems. It's the difference between memorizing recipes and learning to cook.
What this course does differently
This course is organized by pattern, not by loose problems. And, more importantly, it makes you practice before teaching:
- In each pattern lesson, you first get a problem to try solving on your own — you can get it wrong, you can get stuck, that's fine.
- Only then comes the theory. That's when it makes sense, because it answers a difficulty you just felt firsthand.
You'll hit the wall before you get the tool to break through it. That's how learning sticks.
What you need to know about programming
Not much. If you know the basics of Python or JavaScript — variables,
if, loops (for/while), functions, lists/arrays — you can follow along.
All the code runs right here in the browser, in both languages, and you can
edit and run everything. You don't need to install anything.
Don't worry about "knowing everything" before you start. The course introduces each idea when it's needed.
Summary
- LeetCode = problems + automatic test cases; it's used for interviews and for training your reasoning.
- Memorizing solutions doesn't work — learning patterns does.
- This course is pattern-based and makes you try before you learn, so the theory makes sense.
Next lesson: how to read a prompt without panicking and how to get the most out of this course.