LeetCode: Difference between revisions

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{{short description|Online platform for coding interview preparation}}

{{Infobox companywebsite

| name = LeetCode

| logo = [[File:LeetCode Logo black with text.svg|250px]]

| logo =

| type = [[Privately held company|Private]]

| industry = Software

|owner = Leetcode LLC

| founder =

| founded = 7 August 2015

| key_people =

| founder = Winston Tang

| website = https://leetcode.com/

| location_city = [[Palo Alto]], [[California]]

| location_country = [[United States|US]]

| key_people = Hercy Chang (CEO)

| num_employees = 264 (2025)<ref>[https://leadiq.com/c/leetcode/5a6861465700003b015b2278/employee-directory LeetCode Employee Directory, Headcount &amp; Staff] ''LeadIQ''</ref>

|revenue = US$8 million<ref>[https://siliconvalleyjournals.com/company/leetcode LeetCode: Contact Details, Revenue, Funding, Employees and Company Profile]

''Silicon Valley Journal''</ref> (2024)

| website = https://* {{official website|2=leetcode.com/}}

* {{official website||2=leetcode.cn}} (in Chinese)

}}

'''LeetCode''' is an [[online discussion platform|online platform]] for [[Coding interview|coding interview]] preparation. The serviceplatform provides coding and algorithmic problems intended for users to practice [[Software development|coding]].<ref name=nytimes2023/> LeetCode has gained popularity among job seekers in the [[software industry]] and coding enthusiasts as a resource for technical interviews and coding competitions.<ref name=":0nytimes2023">{{Cite web |last=Ansari |first=Tasmia |date=2022-11-17 |title=The Ultimate Guide to Cracking Data Science Interviews |url=https://analyticsindiamag.com/the-ultimate-guide-to-cracking-data-science-interviews/ |access-date=2023-06-10 |website=Analytics India Magazine |language=en-US}}</ref><ref>{{Cite web |last=Kolakowski |first=Nick |date=2022-12-08 |title=Which Programming Languages Are Growing? |url=https://www.dice.com/career-advice/which-programming-languages-are-growing |access-date=2023-06-10 |website=Dice Insights |language=en}}</ref><ref name=nytimes2023>{{Cite news |last=Singer |first=Natasha |date=2023-04-05 |title=For Lower-Income Students, Big Tech Internships Can Be Hard to Get |work=The New York Times |language=en |url=https://www.nytimes.com/2023/04/05/business/tech-internship-application-grind.html |access-date=2023-08-09 |work=The New York Times |language=en |quote=To gear up for the assessments, many students practice their skills on LeetCode, a free test prep site that offers coding and algorithmic problems, along with detailed solutions. The site also offers premium services. For $35 a month, it gives members access to specific problems that companies like Amazon, Google and Microsoft previously used — and some continue to use — to assess applicants. To keep the questions up-to-date, the test prep service said, it regularly surveys members applying for tech positions.}}</ref><ref name=":0">{{Cite web |last=Ansari |first=Tasmia |date=2022-11-17 |title=The Ultimate Guide to Cracking Data Science Interviews |url=https://analyticsindiamag.com/the-ultimate-guide-to-cracking-data-science-interviews/ |access-date=2023-06-10 |website=Analytics India Magazine |language=en-US}}</ref><ref>{{Cite web |last=Kolakowski |first=Nick |date=2022-12-08 |title=Which Programming Languages Are Growing? |url=https://www.dice.com/career-advice/which-programming-languages-are-growing |access-date=2023-06-10 |website=Dice Insights |language=en}}</ref><ref name="dummies">{{Cite book |last1last=Sonmez |first1first=John |url=https://books.google.com/books?id=rEOvDwAAQBAJ&dq=LeetCode&pg=PA108 |title=Programming Interviews For Dummies |last2=Butow |first2=Eric |date=2019-09-11 |publisher=John Wiley & Sons |isbn=978-1-119-56506-2 |language=en |quote=LeetCode is also a popular site for programmers who want to get up to speed.}}</ref><ref>{{Citation |last=Harper |first=Jocelyn |title=Interview Insight: How to Get the Job |date=2023 |url=https://doi.org/10.1007/978-1-4842-8783-5_4 |work=A Software Engineer’sEngineer's Guide to Seniority: A Guide to Technical Leadership |pages=19–28 |editor-last=Harper |editor-first=Jocelyn |url=https://doi.org/10.1007/978-1-4842-8783-5_4 |access-date=2023-08-11 |place=Berkeley, CA |publisher=Apress |language=en |doi=10.1007/978-1-4842-8783-5_4 |isbn=978-1-4842-8783-5 |quote=LeetCode is a platform that specializes in algorithm questions ranked from “Easy” to “Hard” based on the complexity of the subject and solution. They also have a forum where people share what interview questions they encountered in phone screens and on-site interviews to share with the larger public and to help software engineers prepare. I have been fortunate that the only time that I encountered a LeetCode problem during a screening process was for Amazon. ... On this last interviewing journey, I found myself enjoying practicing algorithm coding questions because I found alternative resources to LeetCode.|url-access=subscription }}</ref> As of 2025, the website has 26.3 million monthly visitors.<ref>[https://www.similarweb.com/website/leetcode.com leetcode.com Traffic analytics, ranking & audience (May 2025)] ''[[Similarweb]]''</ref>

'''LeetCode''' is an [[online discussion platform|online platform]] for coding interview preparation. The service provides coding and algorithmic problems intended for users to practice [[Software development|coding]].<ref name=nytimes2023/> LeetCode has gained popularity among job seekers and coding enthusiasts as a resource for technical interviews and coding competitions.<ref name=":0">{{Cite web |last=Ansari |first=Tasmia |date=2022-11-17 |title=The Ultimate Guide to Cracking Data Science Interviews |url=https://analyticsindiamag.com/the-ultimate-guide-to-cracking-data-science-interviews/ |access-date=2023-06-10 |website=Analytics India Magazine |language=en-US}}</ref><ref>{{Cite web |last=Kolakowski |first=Nick |date=2022-12-08 |title=Which Programming Languages Are Growing? |url=https://www.dice.com/career-advice/which-programming-languages-are-growing |access-date=2023-06-10 |website=Dice Insights |language=en}}</ref><ref name=nytimes2023>{{Cite news |last=Singer |first=Natasha |date=2023-04-05 |title=For Lower-Income Students, Big Tech Internships Can Be Hard to Get |work=The New York Times |language=en |url=https://www.nytimes.com/2023/04/05/business/tech-internship-application-grind.html |access-date=2023-08-09 |quote=To gear up for the assessments, many students practice their skills on LeetCode, a free test prep site that offers coding and algorithmic problems, along with detailed solutions. The site also offers premium services. For $35 a month, it gives members access to specific problems that companies like Amazon, Google and Microsoft previously used — and some continue to use — to assess applicants. To keep the questions up-to-date, the test prep service said, it regularly surveys members applying for tech positions.}}</ref><ref name=dummies>{{Cite book |last1=Sonmez |first1=John |url=https://books.google.com/books?id=rEOvDwAAQBAJ&dq=LeetCode&pg=PA108 |title=Programming Interviews For Dummies |last2=Butow |first2=Eric |date=2019-09-11 |publisher=John Wiley & Sons |isbn=978-1-119-56506-2 |language=en |quote=LeetCode is also a popular site for programmers who want to get up to speed.}}</ref><ref>{{Citation |last=Harper |first=Jocelyn |title=Interview Insight: How to Get the Job |date=2023 |url=https://doi.org/10.1007/978-1-4842-8783-5_4 |work=A Software Engineer’s Guide to Seniority: A Guide to Technical Leadership |pages=19–28 |editor-last=Harper |editor-first=Jocelyn |access-date=2023-08-11 |place=Berkeley, CA |publisher=Apress |language=en |doi=10.1007/978-1-4842-8783-5_4 |isbn=978-1-4842-8783-5 |quote=LeetCode is a platform that specializes in algorithm questions ranked from “Easy” to “Hard” based on the complexity of the subject and solution. They also have a forum where people share what interview questions they encountered in phone screens and on-site interviews to share with the larger public and to help software engineers prepare. I have been fortunate that the only time that I encountered a LeetCode problem during a screening process was for Amazon. ... On this last interviewing journey, I found myself enjoying practicing algorithm coding questions because I found alternative resources to LeetCode. }}</ref>

== Features ==

LeetCode offers both free and premium access options. 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.<ref name=nytimes2023/> The performance of users' solutions is evaluated based on response[[Time_complexity|execution speed]] and solution[[Memory management|memory efficiencyusage]], and is ranked against other submissions in the LeetCode database.<ref name="xingBI">{{Cite web |last=Xing |first=Jessica |title=Here's what job seekers need to know about LeetCode, the coding-skills platform millions of developers use to ace the notoriously difficult technical interviews at firms such as Apple, Amazon, and Google |url=https://www.businessinsider.com/leetcode-coding-test-apple-amazon-google-technical-interview-prep-job-2021-11 |access-date=2023-06-21 |website=Business Insider |language=en-US}}</ref>

Additionally, LeetCode provides its users with mock interviews and online assessments. LeetCode hosts weekly and biweekly contests, each having 4 problems.<ref name="dummies" /><ref name="LeetCodeWebsite">{{Cite web |title=LeetCode - The World's Leading Online Programming Learning Platform |url=https://leetcode.com/ |access-date=2023-10-10 |website=leetcode.com}}</ref> After participating in a contest for the first time, one gets assigned a ranking, which can be found in their profile.<ref>{{Cite web |title=Contest |url=https://leetcode.com/contest/ |access-date=2023-10-10 |website=LeetCode |language=en}}</ref> LeetCode also provides its users with daily challenges, following UTC, with a lucky draw at the end of each month for those who stayed consistent for the month.<ref>{{Cite web |title=What is Daily LeetCoding Challenge?|url=https://leetcode.com/discuss/general-discussion/655704/ |access-date=2023-12-09 |website=leetcode.com}}</ref>

LeetCode supports multiple programming languages, including [[Java (programming language)|Java]], [[Python (programming language)|Python]], [[JavaScript]], and [[C (programming language)|C]].<ref>{{Cite book |last1=Nguyen |first1=Nhan |last2=Nadi |first2=Sarah |title=Proceedings of the 19th International Conference on Mining Software Repositories |chapter=An empirical evaluation of GitHub copilot's code suggestions |date=2022-10-17 |series=MSR '22 |___location=New York, NY, USA |publisher=Association for Computing Machinery |pages=1–5 |doi=10.1145/3524842.3528470 |isbn=978-1-4503-9303-4 |quote=LeetCode questions come with test cases in various programming languages, ... (Python, Java, JavaScript, and C)|doi-access=free }}</ref> The platform features forums where users can engage in discussions related to challenging problems, the interview process, and share their interview experiences.<ref name=dummies/>

LeetCode supports multiplea wide range of programming languages, including [[Java (programming language)|Java]], [[Python (programming language)|Python]], [[JavaScript]], and [[C (programming language)|C]].<ref>{{Cite book |last1last=Nguyen |first1first=Nhan |last2=Nadi |first2=Sarah |title=Proceedings of the 19th International Conference on Mining Software Repositories |chapterlast2=AnNadi empirical|first2=Sarah evaluation|date=2022-10-17 of|publisher=Association GitHubfor copilot'sComputing code suggestionsMachinery |dateisbn=2022978-101-174503-9303-4 |series=MSR '22 |___location=New York, NY, USA |publisherpages=Association1–5 for|chapter=An Computingempirical Machineryevaluation |pages=1–5of GitHub copilot's code suggestions |doi=10.1145/3524842.3528470 |isbn=978-1-4503-9303-4 |quote=LeetCode questions come with test cases in various programming languages, ... (Python, Java, JavaScript, and C) |doi-access=free }}</ref> TheIn platformSeptember features2024, forumsLeetCode whereChina userssupports can[[Huawei]]'s engage{{ill|Cangjie inprogramming discussionslanguage|zh|仓颉编程语言}} relatedfor toall challengingproblems.<ref>{{Cite web |title= |script-title=zh:编程刷题平台 LeetCode 力扣所有题目均已支持华为仓颉语言 |trans-title=All problems, on the interviewprogramming process,practice andplatform shareLeetCode theirare interviewnow experiencessupported in Huawei's Cangjie language |url=https://www.<refsohu.com/a/809062659_114760 name|access-date=dummies2024-12-03 |website=[[Sohu]]}}</ref>

== History ==

The platform features forums where users can engage in discussions related to problems, the interview process, and share their interview experiences.<ref name="dummies" />

LeetCode was founded in [[Silicon Valley]].<ref>{{Cite book |last=吴江编著 |url=https://books.google.com/books?id=ENZqEAAAQBAJ&pg=PT9 |title=高效制胜：程序员面试典型题解 |date=2021-07-01 |publisher=Beijing Book Co. Inc. |isbn=978-7-115-55198-6 |language=zh}}</ref>

== Types of problems ==

LeetCode expanded its operations to China in 2018.<ref name=yicai>{{Cite web |first=Liao |last= Shumin |title=IT Job Interview Prepper LeetCode Pockets USD10 Million From Lightspeed China |url=https://www.yicaiglobal.com/news/it-job-interview-prepper-leetcode-pockets-usd10-million-from-lightspeed-china |access-date=2023-08-16 |website=www.yicaiglobal.com |language=en}}</ref> In 2021, LeetCode secured its first round of funding, receiving a $10 million investment from [[Lightspeed China Partners]].<ref name=yicai/>

Every question on LeetCode has a particular category or tag. Some of the most common tags include [[Array_(data_structure)|arrays]], [[String_(computer_science)|strings]], [[Pointer_(computer_programming)|two pointer]]s, [[Stack_(abstract_data_type)|stack]]s, [[binary search]], sliding windows, [[linked list]]s, [[Tree_(data_structure)|trees]], [[trie]]s, [[backtracking]], [[Heap_(data_structure)|heap]]s, [[priority queue]]s, [[Graph_(abstract_data_type)|graph]]s, [[breadth-first search]], [[depth-first search]], [[dynamic programming]], [[greedy algorithm]]s, [[bit manipulation]], [[Database|database problems]], and math.<ref>{{Cite web |title=NeetCode.io |url=https://neetcode.io/roadmap |access-date=2023-10-10 |website=neetcode.io}}</ref>{{Better source needed|date=October 2023}} As of April 2025, LeetCode offers 3525 questions across its three levels of difficulty; with 873 questions categorized as easy, 1829 as medium, and 823 as hard.<ref name="LeetCodeWebsite" />{{Better source needed|date=June 2024}}

== Types of ProblemsHistory ==

LeetCode was founded in Silicon Valley in 2015 by Winston Tang.<ref>{{Cite web |title=Secretary of State |url=https://bizfileonline.sos.ca.gov/search/business |access-date=2024-03-21 |website=bizfileonline.sos.ca.gov}}</ref><ref name=":1">{{Cite web |last=Curry |first=Rachel |date=2024-06-24 |title=AI is shaping the fate of software engineers, but there is a new way to succeed |url=https://www.cnbc.com/2024/06/24/ai-shaping-fate-of-software-engineers-but-there-is-new-way-to-succeed.html |access-date=2024-06-26 |website=CNBC |language=en}}</ref> After moving to the US from Malaysia in 2005, Tang founded the company, citing his own experiences working at Amazon and Google as inspiration.<ref>{{Cite web |last=Tang |first=Winston |title=AI cannot replace software engineers—take it from someone who fought to become one and now helps others pursue the career |url=https://fortune.com/2024/07/30/ai-cannot-replace-software-engineers-or-threaten-their-careers/ |access-date=2024-07-31 |website=Fortune |language=en}}</ref><ref name=":1" />

Leetcode contains a diverse set of problems from different problem categories. These problems help interviewees prepare for their interviews by testing their algorithm and data structure knowledge. Currently, there are eighteen different categories that an interviwer could test your knowledge in. In no particular order, these are: Arrays, Two Pointers, Stack, Binary Search, Sliding Window, Linked List, Trees, Tries, Backtracking, Heaps/Priority Queues, Graphs, Dynamic Programming, Intervals, Greedy Algorithms, Bit Manipulation, and Math/Geometry.

LeetCode expanded its operations to China in 2018, providing Chinese problems, solutions and forums on its Chinese website ''Likou'' ({{Zh|c=力扣|p=Lìkòu}}).<ref name="yicai">{{Cite web |firstlast=LiaoShumin |lastfirst= ShuminLiao |title=IT Job Interview Prepper LeetCode Pockets USD10 Million From Lightspeed China |url=https://www.yicaiglobal.com/news/it-job-interview-prepper-leetcode-pockets-usd10-million-from-lightspeed-china |access-date=2023-08-16 |website=www.yicaiglobal.com |language=en}}</ref> In 2021, LeetCode secured its first round of funding, receiving a $10 million investment from [[Lightspeed China Partners]].<ref name=yicai/>

In each problem category, there are three levels that a problem could be: easy, medium, and hard. If you are applying for an internship concurrently pursuing your undergraduate degree, then you will most likely encounter easy and medium questions - very rarely, will you be asked a hard leetcode question. If you are applying for a new-graduate offer - meaning that you previously graduated, and you want to work at a company - then you will be asked questions in the medium and hard range. There are 736 easy questions, 1521 medium questions, and 634 hard questions.

== Intuition For Problems ==

== When Are You Ready To Interview ==

Leetcode questions are created to challenge your brain. It can take months before you are ready to start interviewing. Most applicants will be pursuing their undergraduate degree, so they will be concurrently preparing for interviews with leetcode during those four years. In the case that you are not pursuing your undergraduate degree, self-preparation can take months to complete. Leetcode offers monthly study plans to ensure that your brain has all the knowledge it needs to solve any problem an interviewer may give you. Additionally, Leetcode offers an online interview preparation IDE (Integrated Development Environment). In this IDE, you and someone else can take the part of the interviewer and interviewee and prepare for interviews with your friends and colleagues. Furthermore, if someone wants to gauge their overall performance in an interview at any particular moment in time, they can instantiate an Leetcode-style online interview. In this online interview, a timer of one-hour and thirty-minutes is started, and three questions are given. The difficulty of each question is hidden, just as in an actual interview. If someone wants specific questions from a company that they are soon interviewing for, then Leetcode offers a paid subscription and users can identify which company they want their questions to be chosen from. For example, if someone choose Google as their online interview, then Leetcode will only give them questions that Google has asked application from previous interview cycles. Once you have solved multiple questions from real online Leetcode-style interviews, then that is when you know you are ready to start interviewing.

== The Interview Process ==

Depending on which company you are applying for, the amount of leetcode-style assessments that you will encounter can vary from one to five. For example, Google requires applicants to code through a series of five assessments. Three of these assessments are online, while two of them are whiteboard interviews.

Below are the processes that a candidate must follow to enter into the software engineering industry or the quant developer industry. Both positions are highly lucrative and require a great amount of skill.

<u>The Software Engineering Process <\u>

The process to become a software engineer is straightforward. Once you apply, you will be sent an online assessment. This online assessment is not proctored, and it will give applicants their first chance to break into a company. Once an applicant passes the online assessment, they will either be rejected or accepted to take proctored interviews. Proctored interviews typically last anywhere from forty-five minutes to one-hour. In this time, a candidate will be given two Leetcode questions. If the candiate is able to answer both of the questions, then he/she will move on to the next round of interviews. Each company has their own standard for the amount of interviews a candidate must pass before they are offered a position. These interviews can be done in any language that you like. The most typical languages are Python, Java, and C++. You can choose Python for its easy readability and syntax. Data structures in Python are easy to create; however, using them can be a little harder. For example, viewing a stack in a list is not usual. You can choose Java because that was the first language you might have learned at your university. In some circumstances, some jobs will require you to apply with C++. C++ is a fast low-level language that works really close to the hardware. For typical software engineering positions, you won't be working on code that is used that closely to hardware, so the choice of language is ambiguous. However, for positions where you are doing something specific, such as working on low-level systems, C++ is often the best choice.

Once a candidate makes it to a certain level of interviewing, he/she may be asked to complete an onsite interview. An onsite interview takes place at the company headquarters, and the candidate transitions from coding in an IDE to the whiteboard, where he/she will write their solution directly in front of engineers who currently work at that company.

<u>The Quantitative Developer Process <\u>

== See also ==

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== References ==

<references />

[[Category:Educational websites]]

== External links ==

* {{Official website}}

[[Category:American educational websites]]

[[Category:Programming contests]]

[[Category:Computer science competitions]]

[[Category:Software developer communities]]

<references />{{compu-website-stub}}