Hard data structure and algorithm practice puzzle.
Given a sorted array that's been rotated at some unknown point, like [4, 5, 6, 7, 0, 1, 2], return the index of the target, or -1. Binary search still works. At every middle, one half is always in sorted order. Check whether the target falls in that half, and throw away the other half. You never need to find the rotation point.
Solve it three ways: snap the jigsaw pieces together, fill in the blanks, or type it from scratch against the tests. This one is free.
Every line of the solution comes with a note explaining why it is there, and a step by step replay shows the code running. At level 3, where you type it yourself, you can ask for an AI mock interview on this problem that ends with a hiring manager's scorecard.
Then grow it into a real project with the Software Engineer button: this puzzle becomes the Event Quantile Rig, a pipeline you can run and download. See every Software Engineer project.
Browse all 576 puzzles