Medium data structure and algorithm practice puzzle.
Given an array, sort it with selection sort. Find the smallest value in the unsorted part, swap it to the front of that part, and repeat. It always takes O(n squared) comparisons, but it never makes more than n swaps. That makes it useful when writing is much more expensive than reading, like on flash memory.
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 Calibrator, a pipeline you can run and download. See every Software Engineer project.
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