Easy data structure and algorithm practice puzzle.
Given a player's rating deviation, their volatility, and how many rating periods they sat out, return their new deviation, rounded to two decimal places. Every quiet period makes the ladder a little less sure of them, and more so for an erratic player. Never go past 350, the deviation of a brand new account. A rating is evidence, and evidence goes stale.
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 Match Smoothing Rig, a pipeline you can run and download. See every Software Engineer project.
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