LeetCode

LeetCode, LLC d/b/a LeetCode is an online platform for coding interview preparation. The service provides coding and algorithmic problems intended for users to practice coding. LeetCode has gained popularity among job seekers and coding enthusiasts as a resource for technical interviews and coding competitions.

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. The performance of users' solutions is evaluated based on response speed and solution efficiency, and is ranked against other submissions in the LeetCode database.

Additionally, LeetCode provides its users with mock interviews and online assessments. LeetCode hosts weekly and biweekly contests, each having 4 problems. After you participate in a contest for the first time, you get assigned a ranking, which can be found in the profile. 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.

LeetCode supports multiple programming languages, including Java, Python, JavaScript, and C. The platform features forums where users can engage in discussions related to problems, the interview process, and share their interview experiences.

Types of problems
Every question on LeetCode has a particular category or tag. Some of the most common tags include arrays, strings, two pointers, stacks, binary search, sliding windows, linked lists, trees, tries, backtracking, heaps, priority queues, graphs, breadth-first search, depth-first search, dynamic programming, greedy algorithms, bit manipulation, database problems, and math. In total, LeetCode offers 3199 questions across its three levels of difficulty; with 801 questions categorized as easy, 1679 as medium, and 713 as hard.

History
LeetCode was founded in Silicon Valley in 2015 by Winston Tang.

LeetCode expanded its operations to China in 2018. In 2021, LeetCode secured its first round of funding, receiving a $10 million investment from Lightspeed China Partners.