LeetCode

What LeetCode Is

LeetCode is an online platform for practicing the algorithm and data structure problems used in software engineering interviews. Wikipedia describes it as "an online platform for software coding interview preparation" whose site "provides algorithmic problems intended for users to learn and practice programming." It is a learner product, but for a specific learner: someone who can already code and needs to get fast and reliable at interview-style problems. A review on dataquest.io puts it plainly: "It's not really a learning platform. It's where you go when you already know how to code and need to get good at the kind of problems that show up in technical interviews."

According to Wikipedia, LeetCode was founded in Silicon Valley in 2015 by Winston Tang, is owned by Leetcode LLC and is headquartered in Palo Alto, California. It expanded to China in 2018 with a Chinese site, Likou (力扣), offering Chinese problems, solutions and forums, and in 2021 it took its first funding round, a $10 million investment from Lightspeed China Partners. Wikipedia also cites a traffic estimate of 26.3 million monthly visitors as of 2025.

This entry is written from those third-party sources (Wikipedia and reviews on dataquest.io, spacecomplexity.ai, educative.io and programiz.pro); each fact is attributed to the page that states it.

The Problem Bank

The core of LeetCode is a large, searchable bank of problems. Wikipedia says every question carries a category or tag, with common tags including arrays, strings, two pointers, stacks, binary search, sliding windows, linked lists, trees, tries, backtracking, heaps, priority queues, graphs, breadth-first and depth-first search, dynamic programming, greedy algorithms, bit manipulation, database problems and math. Problems come in three difficulty levels. Wikipedia, citing a source it marks as needing a better reference, gives a January 2026 count of 3816 questions: 922 easy, 1922 medium and 902 hard. The review pages give rounder figures: spacecomplexity.ai and programiz.pro both describe "over 3,000" or "3,000-plus" problems.

Practice happens in the browser. A learner picks a problem, writes a solution in one of the supported languages, and submits it. Wikipedia lists Java, Python, JavaScript and C among the supported languages, and notes that the Chinese site has supported Huawei's Cangjie language for all problems since September 2024. Wikipedia also explains how submissions are judged: "The performance of users' solutions is evaluated based on execution speed and memory usage, and is ranked against other submissions in the LeetCode database."

The dataquest.io review describes the teaching style as close to none, by design: "LeetCode throws full problems at you. There is almost no scaffolding. You internalize common solution templates and learn to pick the right approach fast." It is, in the same review's words, "self directed with strong community support," with discuss threads, company tags and contests to help when a learner gets stuck.

Contests, Daily Challenges and Study Plans

LeetCode adds structure through competition and routine. According to Wikipedia, it "hosts weekly and biweekly contests, each having 4 problems," and after a first contest each participant gets a ranking shown on their profile. spacecomplexity.ai says those contests "give you a ranking that correlates with interview performance."

Wikipedia also describes daily challenges that follow UTC, "with a lucky draw at the end of each month for those who stayed consistent for the month." For learners who want a path rather than a pile of problems, the dataquest.io review notes that "the platform includes study plans, timed contests, and company-specific question sets," and programiz.pro mentions "study plans for specific topics like DSA and System Design" and interview questions selected for top companies like Facebook and Apple.

Community and Discussion

Each problem has a discussion area. Wikipedia says the platform "features forums where users can engage in discussions related to problems, the interview process, and share their interview experiences." spacecomplexity.ai credits LeetCode with "a community that has dissected every problem in exhaustive detail" and adds that its discussion sections are sometimes the clearest explanation available for a hard problem. The dataquest.io review says "the community explanations are detailed."

Mock Interviews and Assessments

Wikipedia states that "LeetCode provides its users with mock interviews and online assessments." The reviews are less enthusiastic about this part. spacecomplexity.ai calls the built-in mock interview mode "surface-level," and the dataquest.io review says Premium "mainly adds company tagged questions and interview simulation tools for focused preparation."

Free Access and Premium

LeetCode has both free and paid access. Wikipedia: "While free users have access to a limited number of questions, premium users gain access to additional questions previously used in interviews at large tech companies." The dataquest.io review calls it "heavily usable for free," saying "You can solve a large set of problems without paying," with free access covering the core problem set.

Sources give different Premium prices, so each is quoted with its source:

• The dataquest.io review's pricing table lists LeetCode at $39/month, or $179/year (about $14.92 a month).
• spacecomplexity.ai (May 2026) gives Premium as $160/year and describes its value as company-tagged problems filtered to the last six months of activity: "That frequency data, filtered to the last six months, is the real value of Premium."
• A New York Times article from 2023, quoted in Wikipedia's references, put it at "$35 a month" for access to problems companies such as Amazon, Google and Microsoft had used to assess applicants. The same article says that to keep questions current, LeetCode "regularly surveys members applying for tech positions."

Anyone about to subscribe should check the current price on LeetCode's own pricing page.

What Reviewers Say

The dataquest.io review gives LeetCode a rating of 2.7/5 and sums up the reception: "The problem bank is huge, the community explanations are detailed, and many candidates say it helped them pass interviews they would have failed before." It also records the complaints: some users feel it "turns studying into pattern memorization and endless counting of solved problems," and others mention "burnout, pressure from rankings, and frustration with paid features." It quotes a user, Valery Tretyak: "Lots of clear problems, good catalogue with filters, great editorial explanations," adding that "Most Explore topics are good, but some are outdated and poorly structured."

educative.io's blog makes a related point about scale. Its author recalls LeetCode having "about 200 interview questions" around 2011 and "2,800 questions" at the author's last check, and argues that trying to "churn through as many LeetCode problems as possible" is "not a scalable prep strategy anymore." spacecomplexity.ai suggests targeting "75 to 150 problems across core pattern families, timed" during the problem practice phase.

Who It Suits

LeetCode suits a working developer or a computer science student with an interview coming up: someone who can already write code in Java, Python, JavaScript or C and wants timed, judged practice on the problem types interviewers use. It suits learners who are motivated by rankings, contests and a daily streak, and those who want to read several solution approaches from other users after solving a problem. The free tier is large enough to start without paying; Premium is aimed at candidates who want company-tagged questions.

It does not suit a beginner learning to program. The dataquest.io review says, "If you're still learning the basics, come back to this one later," and notes that it trains "speed, edge case thinking, and interview stamina, but not system design or project work." Learners who want lessons, projects or a guided course will find little scaffolding here, and those prone to burnout should take the reviewers' warnings about ranking pressure seriously.