Easy data structure and algorithm practice puzzle.
Given [visitors, buyers], return the percentage of visitors who bought, rounded to the nearest whole number. So [200, 50] is 25. Divide buyers by visitors, multiply by 100, then round. In languages with integer division, divide as a decimal first, or every answer under 100 percent comes out as 0.
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 Order Retention Curve, a pipeline you can run and download. See every Software Engineer project.
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