Hard data structure and algorithm practice puzzle.
Fares are published one per day. Given the daily fares, return for each day how many days you'd have to wait for a strictly cheaper fare. If a cheaper fare never comes, use 0. Checking every later day for every day is the slow way.
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 first stage of a pipeline you can run and download. See every Software Engineer project.
Browse all 576 puzzles