Easy data structure and algorithm practice puzzle.
Given a sorted array and a target, return the target's index, or -1 if it isn't there. Look at the middle. If the target is bigger, throw away the left half. If it's smaller, throw away the right half. Every check cuts what's left in half, which is why a database index can find one row in a billion in about 30 steps.
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 Read Quantile Rig, a pipeline you can run and download. See every Software Engineer project.
Browse all 576 puzzles