Medium data structure and algorithm practice puzzle.
Given a list of build inputs like the source and the compiler flags, return one 32-bit cache key. Sort the parts first, so the same flags in a different order give the same key. Then FNV-1a hash each part's characters, followed by a '|' separator, so "ab" then "c" can't collide with "a" then "bc". A cached compile is only safe to reuse when every input that could change it matches.
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 Trip Search Index, a pipeline you can run and download. See every Software Engineer project.
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