Easy data structure and algorithm practice puzzle.
Everyone starts at level 1, and thresholds[i] is the total XP needed to reach level i + 2, in increasing order. Given a player's experience points, return their level: 1 plus how many thresholds they've reached, where reaching one exactly counts. Use binary search for the first threshold above their XP, since a level curve can have hundreds of entries and this runs every time XP is earned.
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 Entity Ordered Index, a pipeline you can run and download. See every Software Engineer project.
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