Coding exercises

Remove duplicate values while preserving first-seen order.

The classic warm-up: map numbers to Fizz, Buzz, or FizzBuzz.

Use a closure to make independent counters that remember their own state.

Flatten an arbitrarily nested array of numbers into a flat list.

Bucket items into a record keyed by a function of each item.

Select just the active users from a table.

Return the three most expensive products, priciest first.

Total each customer's spend across their orders.

Add up a list of numbers — your first Python function.

The classic, in Python — loops, modulo, and str().

Count how often each word appears (case-insensitive) into a dict.