Coding interview · Python and JavaScript
685 original problems grouped by the 20 patterns interviewers test. Write Python or JavaScript in the browser with a built-in terminal, then follow a step-by-step walkthrough from brute force to optimal.
How it works
Each pattern starts with when to use it and the idea behind it, then problems from easy to hard.
Python or JavaScript, run against the examples in a built-in terminal, then submit against hidden tests.
Clarifying questions, the brute force, the key insight, the optimal steps and a dry run, in that order.
The patterns
Most interview problems are a known pattern in disguise. Learn to spot it and the solution follows.
Try one
Free, and the same format as every problem in the bank.
EasyArrays & Hashing
You are given an array of integers nums and an integer target. Exactly one pair of different positions i and j holds values that add up to target.
Return the two indices as [i, j] with i < j.
nums[2] + nums[3] = 1 + 6 = 7.
The two 5s sit at different positions, so they form a valid pair.
Free and Pro
The first three Easy problems of every pattern: 60 problems with the editor, the terminal, hints and the full walkthrough.
All 685 problems, every walkthrough and the reference solutions in Python and JavaScript. The same Pro plan also unlocks every certification exam.
Your next interview is a pattern you can learn.
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