Definition
LeetCode is an online platform for programming practice that offers algorithm problems, online judging and coding contests, widely used for technical interview preparation. According to Wikipedia, LeetCode was founded in Silicon Valley in 2015. See the official site.
How it works
Users pick problems from the problem set by difficulty or tags (arrays, strings, two pointers, binary search and so on), write and submit code in the editor, and the platform evaluates solutions on execution speed and memory usage, ranking them against other submissions. Multiple languages are supported, including Java, Python, JavaScript and C. The platform runs weekly and biweekly contests, a daily challenge and discussion forums. Access comes in free and Premium tiers: free users have access to a limited set of questions, while Premium adds more, including questions previously used in interviews at large tech companies (platform mechanics as described by Wikipedia).
Usage
Algorithm practice and technical interview preparation are the primary uses; curated lists such as the “Hot 100” are common practice paths. Contests exercise timed problem-solving and produce rankings, and job seekers use the platform to get familiar with the question styles of target companies. For developers working on AI applications, it also serves as one way to keep coding fundamentals sharp.
Related and confusable terms
- LeetCode vs. Likou (leetcode.cn): Likou is LeetCode’s Chinese site, which, according to Wikipedia, launched for the Chinese market in 2018 with Chinese problems, solutions and forums; the two sites’ problem sets and operations are not identical.
- LeetCode vs. LeetCode Premium: the paid tier unlocks additional problems (including past big-tech interview questions) on top of the free tier’s core practice features.
- “Grinding problems” vs. LeetCode: grinding refers to repeatedly doing coding exercises in general; LeetCode is one of the most common platforms, not the only one.
In this episode
In Weekly #007, in the chapter “什么值得学：向 AI 提问与真实的人际交流” (What is worth learning: asking AI questions and real human connection), 橘子 (Orange) retells a V2EX post in which the author gave up grinding LeetCode, spent two months learning social skills, never got interviews with the FAANG companies, but gained a girlfriend and became much happier. This is the show retelling a community post, not an assessment of the platform. See the episode 007 chapter (Chinese transcript).
Frequently asked questions
What is LeetCode?
An online algorithm-practice platform: a problem set with online judging, where submissions are evaluated on execution speed and memory and ranked against others, commonly used for technical interview preparation. See the official site.
Is LeetCode free?
The platform has free and Premium tiers: free users can work on part of the problem set and join contests, while Premium unlocks additional problems, including past big-tech interview questions. Current benefits are described on the official site.
What is the relationship between LeetCode and Likou?
Likou (leetcode.cn) is LeetCode’s Chinese site; per Wikipedia it expanded to China in 2018 with Chinese problems, solutions and forums. Users who prefer a Chinese interface usually use Likou.
How do you pronounce LeetCode?
It is commonly read as the English words “Leet-Code” (“leet” being a hacker-culture spelling of elite); Chinese-speaking communities also often just say “Likou”. (Editorial supplement: leetcode怎么读 comes from real search suggestions; the pronunciation note is editorially added.)