The Raw Truth About Leetcode Cheat Sheets
You'll find hundreds of them online. PDFs, Notion templates, Anki decks, GitHub repos that haven't been updated since 2021. Most of them are just lists of problems dumped into categories with no real structure. I spent about three weeks last year going through the top-ranking Leetcode Cheat Sheet results before I realized the few that actually helped were the ones I built myself and kept editing constantly. Here's how to make one that doesn't waste your time.
Leetcode Cheat Sheet: What Actually Works
A functional cheat sheet isn't a problem list. It's a pattern index. You categorize by technique, not by difficulty or tag. The top tags on Leetcode — Dynamic Programming, Greedy, Graph, Depth First Search — look useful until you realize that "Dynamic Programming" covers everything from Fibonacci sequences to subset sum to edit distance, and none of those problems share the same mental model. Your cheat sheet should group by recurrence type, state definition, and boundary conditions. I built mine in plain text with a simple hierarchy. Pattern name first, then the canonical problem it maps to, then a one-line note on the trick. Something like: Sliding Window Max Sum Subarray of Size K
Trick: right pointer advances freely, left only when window exceeds K. Don't overthink the inner loop.
This format forces you to extract the insight, not just copy a solution. That extraction is where the actual learning happens.
Get the Full Details
What to Include
Start with the patterns that show up most frequently across interviews at the companies you're targeting. For FAANG-level roles, the core set breaks down like this: TWO POINTERS — paired, opposing, or fast/slow. The slow/fast pointer variant for cycle detection alone covers probably ten different problem permutations. You don't need ten entries. You need one solid entry with the variant sub-types listed underneath. HASH MAP / HASH SET — looking up complements, counting frequencies, tracking seen elements. The edge case people miss here is duplicate key handling. I once spent twenty minutes debugging a "find all anagrams" solution because I was using a single hash map instead of two. The cheat sheet entry should flag that explicitly.
SLIDING WINDOW — fixed size, variable size, two-pointer expansion. The variable-size variant is where most people stall because they conflate it with the fixed-size version. Fixed size has a clean O(n) single pass. Variable size needs conditional shrinking logic that trips people up constantly. DYNAMIC PROGRAMMING — this deserves its own section and probably half your cheat sheet. Start with 1D DP (climbing stairs, house robber), move to 2D DP (grid paths, edit distance), then touch on knapsack variants. The most important note you can add: identify whether you're optimizing for a value or counting possibilities. These produce completely different recurrence relations even when the problem structure looks identical. DEPTH FIRST SEARCH / BREADTH-FIRST SEARCH — DFS for traversal and backtracking. BFS for shortest path on unweighted graphs. The thing nobody puts on their cheat sheet but should: iterative DFS requires an explicit stack and careful state management. Recursive DFS is simpler but risks hitting recursion limits on large inputs. I switched to iterative after a Leetcode problem with a deep tree caused a stack overflow on their judge. Took me three attempts to get the iterative version right.
TREE / GRAPH — these overlap heavily. Union-Find belongs here. Topological sort belongs here. Binary search tree properties belong here. Group them by operation type rather than data structure type.
What to Leave Out
Don't include problems you can solve without thinking. If you can write the solution in under two minutes on the first try, it doesn't belong on the cheat sheet. The purpose is to capture the hard-won patterns, not to archive every problem you've ever solved. Don't include full solutions. Include the approach and the gotcha. A complete code example defeats the purpose because you're memorizing syntax instead of internalizing the pattern.
Common Mistakes
The biggest mistake I see people make is treating the cheat sheet as a pre-interview cram tool. It should be a living document you update after every practice session. If you solve a problem that introduces a new variation of an existing pattern, the cheat sheet entry should reflect that. If you struggle with a pattern, the entry should note exactly where you got stuck. Another mistake is not accounting for time and space complexity analysis. Every entry should have a quick complexity note. Interviewers ask this even when you're not explicitly solving a problem — they're checking whether you think about efficiency at all. A one-line notation like O(n) time, O(1) extra space saves you from sounding unsure when they press you on it. Also worth noting: some patterns have constraints that make them useless in certain contexts. Knapsack DP, for example, becomes impractical when the weight values are large because the state space explodes. I learned this the hard way during a mock interview where I confidently proposed a DP solution that would have timed out on the given constraints. The interviewer's follow-up question about the state space size exposed it immediately. Your cheat sheet should flag these limitations so you don't walk into an interview blindly trusting a pattern.
How to Use It
Review it once a week, not the night before an interview. Spaced repetition matters. Go through each pattern and try to reconstruct the canonical problem from memory without looking. If you can't, that's a gap. Add a more detailed note to that entry. When practicing new problems, work backward from the pattern. Before reading a problem, glance at your cheat sheet. Pick a random pattern and try to recall its canonical form. Then solve a problem that matches. This reverse approach builds pattern recognition faster than the standard forward method of solving problems and hoping they reinforce the patterns. The sheet itself should live somewhere you can access it quickly. I used a local Markdown file synced to my phone. Others prefer Notion. The tool doesn't matter. Consistency does. A cheat sheet you look at once and never touch is worse than no cheat sheet at all.
