Easy data structure and algorithm practice puzzle.
Given a temperature in Kelvin, return it in Celsius by subtracting 273. Both scales use the same size degree. They only disagree about where zero is. Zero Kelvin is absolute zero, the coldest anything can get, so Kelvin never goes negative. Celsius can.
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 Ledger Balancer, a pipeline you can run and download. See every Software Engineer project.
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