Blind 75 is the most referenced LeetCode shortlist for interview prep—75 canonical problems that cover the core patterns. Here’s what it is, why it matters, how it’s structured, and a practical system to learn it without burning out.
If you’ve spent any time prepping for coding interviews, you’ve heard the phrase Blind 75. It pops up in Reddit threads, Medium posts, and friend group chats like a shared survival code: “Just finish Blind 75 and you’ll be fine.”
But what is Blind 75, really? Why has it become the de-facto checklist for the DS&A portion of interviews? And if you’ve already tried it once and stalled somewhere around problem #19, what would it take to come back and actually master it—without memorizing solutions you’ll forget next week?
This post breaks down the what/why/structure of Blind 75, then gives you a practical plan to learn it the way hiring signals are actually evaluated: not by streaks, but by clarity, adaptability, and edge-case thinking. We’ll end with a lightweight way to embed those habits directly on the LeetCode page using LeetCopilot so you keep momentum without tab-switching gymnastics.
What is Blind 75?
Blind 75 is a curated set of seventy-five LeetCode problems that collectively cover the fundamentals tested in most software engineering interviews. Think of it as an 80/20 bundle: a small list aimed at covering the major patterns you’ll see again and again—arrays, strings, hash maps, two pointers, sliding window, linked lists, trees/graphs with BFS & DFS, heaps, intervals & sorting, backtracking, dynamic programming (DP), binary search, union-find, and a few math/prefix-sum staples.
It’s not an official list from LeetCode or any particular company. It emerged from the community as candidates compared notes on what actually showed up in phone screens and onsites. Over time, the list stabilized into a practical “core”—not exhaustive, not perfect, but focused.
Why it stuck:
- Scope you can finish. 75 feels achievable compared to “do 300 problems.”
- Pattern coverage. It’s broad enough to prevent holes, narrow enough to build rhythm.
- Shared reference. Study buddies, mentors, and forum posts can talk about the same set.
Why Blind 75 matters
If you strip interviews down to their essence, most coding rounds test three things:
- Pattern recognition under pressure. Do you see the family (e.g., “this smells like sliding window with a frequency map”)?
- Implementation clarity. Can you turn ideas into clean code with invariants that hold?
- Edge-case instinct. Can you break your own happy path before the interviewer does?
Blind 75 puts you in repeated contact with those core experiences. Because the problems are canonical, you get reps that generalize. You also calibrate difficulty, pacing, and communication patterns—skills that are hard to build by grinding random questions in isolation.
Structure and characteristics: what’s inside the 75
Every variant of the list differs a bit, but the shape tends to look like this:
- Arrays & Strings (large chunk): frequency maps, two pointers, sliding window, sorting + greedy sweeps, prefix sums.
- Linked Lists: reversal patterns, fast/slow pointers, cycle detection, merge k lists.
- Trees & Graphs: BFS for shortest paths/levels; DFS for recursion/backtracking; topological sort; connected components/union-find.
- Heaps & Intervals: meeting rooms, k-most/frequent, “merge intervals” flavors.
- Stacks/Monotonic Structures: next greater element, daily temperatures, area in histogram.
- Binary Search: on arrays and on answer space (min feasible value).
- Dynamic Programming: 1D/2D tabulation, subset/knapsack, LIS, edit distance, coin change.
- Math & Misc: bit tricks, fast power, random pick, reservoir sampling here and there.
Difficulty profile: mostly easy/medium with a handful of hard problems that are more about composition of prior patterns than brand-new ideas.
What repeats: invariants (what must always be true in your window/stack), state design (what to remember across steps), and the habit of writing & checking edge cases early.
Why so many people struggle with Blind 75
You don’t fail Blind 75 because you’re “bad at algorithms.” You fail because of process traps:
- Memorization over mastery. Copying a solution “to learn it” becomes a habit; a week later, it’s gone.
- Silent practice. You never practice explaining, yet interviews grade explanation.
- No edge-case drills. You pass sample tests and move on; the next interviewer’s case shatters your approach.
- Zero review system. Without spaced repetition and notes you’ll actually read, retention decays.
- High friction. You keep copying prompts and code into a separate chat; focus crumbles.
The fix isn’t “more problems.” It’s a better loop for each problem: progressive hints, early edge-case pressure, quick visualization when stuck, micro-notes for later review, and weekly reps at speaking your thoughts.
A practical system to actually learn Blind 75
Below is a structure I’ve seen work for candidates at every level—from graduates to senior devs coming back to interviews after years on the job. It’s not about heroics; it’s about designing fewer, better reps.
1) Use progressive hints (without spoilers)
Treat hints as a three-rung ladder and climb only as high as needed:
- Strategy: nudge toward the right family (e.g., “this problem wants a growing/shrinking window”).
- Structure: outline moving parts (map, two indices, invariant), but not the code.
- Checkpoints: surgical questions that expose blind spots (“what happens when duplicates collide at the right pointer?”).
If you’re working with a friend or an assistant, be explicit: “strategy-level hint only—no code.” Your goal is to protect the reps that build intuition while avoiding tailspins.
2) Make bugs show up early (edge-case drills)
Right after the first green check, ask: “What 3 inputs would embarrass this solution?” Then generate and batch-run them. When something breaks, fix it and capture the failure in a one-line note (“window must jump past last occurrence, not step by one”).
This swaps “I hope it’s correct” for “I already tried to break it,” which is exactly the pressure interviews apply.
3) Visualize when your brain stalls
For recursion, pointers, or mutable structures, watch the code execute: call-stack expansion, pointer motion, queue contents. Thirty seconds of stepping through can beat five minutes of rereading the same paragraph.
4) Turn today’s effort into tomorrow’s memory (micro-notes)
After each problem, spend two minutes on a tiny template you’ll actually use:
- Problem in one sentence
- Approach in two
- Invariant in one
- Failure mode you hit + fix
Tag it (array/window/graph/DP). Schedule Day-3 / Day-7 / Day-30 reviews. Before each review, try the problem cold for 10 minutes; only then peek at your note.
5) Practice performance, not just solving
Once a week, do a 30-minute mock (one medium + one easy). Narrate: restate, approach, complexity target, invariant, edges, test. Accept one strategy hint if stuck past 7 minutes. The goal isn’t to “win” the mock—it’s to find what to train next week (clarity, pacing, or edge-case instincts).
6) Reduce friction to raise reps
If every help action means copying the prompt and pasting code into another window, you’ll avoid getting help until you’re frustrated. The ideal flow lives inside the LeetCode page: ask for a nudge, generate test inputs, run them, visualize, and save a micro-note—without leaving the editor.
A three-week plan to get through (and remember) Blind 75
This is a template; tweak for your schedule. The point is cadence and compounding, not heroics.
Week 1 — Foundations & Rhythm
- Pick 14 problems covering arrays/strings + one tree/graph.
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Daily cadence (60–90 min):
- 2 problems with progressive hints (stop as soon as you solve; don’t “finish the code” if the idea is solid).
- Batch-run edge cases on both.
- One 30-second visualization for the stickier one.
- Two-minute micro-note each.
End of week: short mock (one medium + one easy). Identify the weak link: clarity, time boxing, or edges.
Week 2 — Breadth & Pressure
- Add 14 more: linked lists, heaps/intervals, stack/monotonic, binary search.
- Keep the same daily cadence; enforce hint discipline.
- Midweek: 20-minute DP primer (state, transition, base, order). Do two light DP problems with structure-level hints only.
- End of week: mock again. If you’re still narrating reactively, practice the talk-track: restate → constraints → naive baseline → target complexity → invariant → data structures → plan.
Week 3 — DP Focus & Consolidation
- Focus set: 10 DP problems (coin change, rob house, LIS, edit distance).
- For each: state the state (what you remember), the transition (how it moves), and why the order matters.
- Daily: 1–2 DP + 1 review redo from Weeks 1–2.
- End of week: full 30-minute mock; close with a five-minute “teach back” of a problem you now own.
At the end of three weeks you won’t “know everything,” but you’ll have the habits and artifacts (notes, test sets, talk-track) that turn the rest of Blind 75 from grind into momentum.
FAQ quick hits
Q: Do I have to finish all 75 before interviewing?
A: No. Many candidates stabilize after ~40–50 well-learned problems if they’ve built the habits above. Quality beats quantity.
Q: How many hints are too many?
A: If you’ve climbed past checkpoint-level twice and still feel lost, stop. Study a clean solution now and redo it tomorrow cold.
Q: What about solution videos?
A: Useful after you’ve tried. Treat them like a post-mortem, not a first resort.
Q: Should I timebox?
A: Yes. 15 minutes to frame/attempt; take a strategy hint if still stuck. Another 10 minutes to adapt; escalate once. After 40–50 minutes overall, pivot to learning mode.
How LeetCopilot plugs into this system (without getting in your way)
You can do everything above with pen, paper, and iron will. Most of us don’t have infinite willpower, which is why embedding the workflow inside the LeetCode page helps:
- Ask for progressive hints that respect your ladder (strategy → structure → checkpoint) without spoilers.
- Generate and batch-run tricky inputs the moment you pass the first test, so bugs surface early.
- Visualize execution when recursion or pointer logic goes gray.
- Save two-minute micro-notes right where the insight happened; they reappear on review days.
- Run a quick interview-style session to practice the talk-track and get feedback on clarity and approach.
The point isn’t to outsource thinking. It’s to protect the reps that matter—by removing the friction and drift that usually derail them.
Closing thoughts
Blind 75 is popular for a reason: it’s the smallest coherent set that covers most interview patterns without swallowing a year of your life. But a checklist alone won’t get you hired. The candidates who convert practice into offers are the ones who:
- nudge instead of spoil,
- break their code on purpose,
- visualize when stuck,
- write notes they’ll actually read, and
- practice speaking their thinking.
Do that, and Blind 75 stops being a mountain and starts being a path.
If you want those habits to live where you already work, try keeping everything in-page.
Give LeetCopilot a spin—progressive hints, edge-case runs, quick visualizations, and notes that turn reps into memory, all without leaving LeetCode.
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