LeetCode for Beginners: 10 Tips to Go From 0 to 100 Problems Solved

Starting LeetCode feels like staring at a wall. You open your first medium problem, read it three times, and still have no idea where to begin. You're not alone — every engineer who has cracked a FAANG interview went through the exact same thing. The difference is they stuck with a system.

Here are 10 tips that will take you from complete beginner to 100 problems solved without burning out.

1. Start with Easy problems — but not randomly

Resist the urge to pick random Easy problems. Instead, follow a curated list like the Blind 75 or NeetCode 150. These lists are specifically designed so that each problem teaches a reusable pattern, not just a one-off trick.

Starting randomly means you'll end up solving five variations of the same string reversal while missing the sliding window pattern entirely. Curated lists give you maximum coverage in minimum time.

2. Master one data structure at a time

Don't context-switch between arrays, trees, graphs, and dynamic programming in the same week. Pick one topic, solve 10–15 problems in it, and only then move on.

The order that works well for most people:

1. Arrays and strings
2. Hash maps and sets
3. Two pointers
4. Sliding window
5. Stack and queue
6. Binary search
7. Trees (BFS, DFS)
8. Graphs
9. Dynamic programming

3. Spend at most 20–30 minutes before looking at hints

Struggling is good. Staring at a blank screen for two hours is not. If you haven't made meaningful progress after 20–30 minutes, look at the hint or the solution approach (not the code). Try to implement the approach yourself before reading any code.

This is the single most effective way to accelerate learning. Reading a solution cold teaches you almost nothing. Struggling first, then seeing the answer, creates a lasting memory.

4. Write your solution before submitting

Type your solution in a local editor, trace through it manually with a small example, and only then paste it into LeetCode. This forces you to think rather than "submit and debug by error message."

Interviewers will notice if you can trace through your own code. Practice this from day one.

5. Understand time and space complexity for every problem

After solving a problem, always answer two questions:

• What is the time complexity of my solution?
• What is the space complexity?

Then check if a more optimal solution exists and understand why it's faster. The first solution you write will often be O(n²). Learning to see the path to O(n) is the core skill LeetCode is training.

6. Don't memorize — recognize patterns

There are roughly a dozen core patterns that cover 80% of LeetCode problems:

• Two pointers — sorted arrays, finding pairs
• Sliding window — contiguous subarray problems
• Fast & slow pointers — cycle detection in linked lists
• Merge intervals — overlapping range problems
• Cyclic sort — problems involving 1 to N
• BFS/DFS — tree and graph traversal
• Dynamic programming — optimization with overlapping subproblems
• Backtracking — permutations and combinations

When you open a new problem, your first question should be: which pattern does this smell like? That recognition is what gets you from "no idea where to start" to "I know the structure, I just need to figure out the details."

7. Revisit problems you got wrong

Tag every problem you couldn't solve without hints. Come back to it one week later and try again from memory. If you fail again, redo it and revisit in two weeks. This spaced repetition turns shaky understanding into reliable recall — exactly what you need in a live interview with someone watching you.

8. Solve the same problem in multiple ways

Once you solve a problem, ask: is there another way? Most medium problems have a brute-force O(n²) solution and an optimal O(n) or O(n log n) solution. Understanding both, and being able to articulate the trade-offs, is a strong signal to interviewers.

9. Practice explaining while you code

Silent coding is comfortable. Interviews are not silent. Get comfortable narrating your approach as you type. "I'm going to use a hash map to store frequencies here because lookup is O(1)…" Practice this alone if you have to. The verbal component is a separate skill from the coding skill, and it needs separate practice.

10. Aim for consistency, not volume

Ten problems per week for three months is dramatically better than 50 problems in one week and then nothing for six weeks. Set a realistic daily goal — even one problem — and protect it. Momentum compounds. After three months of consistent practice, the mental model for pattern recognition becomes largely automatic.

A note on tooling

Once you can reliably solve problems on LeetCode's own editor, consider practicing in a plain text editor with no autocomplete. This mirrors actual interview conditions more closely. Some engineers also use tools to capture problems by screenshot and generate solutions to study different approaches — useful for review, less so as a substitute for practice.

The fundamentals are non-negotiable. Get comfortable with the patterns first, then use every advantage available to you when it counts.

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