Set으로 고유 항목 다루기

When you only care whether something is present, not how many times, use a Set. It holds each item once. ✨

A Set takes a single element type in brackets, like Set[Int]. Every member shares that type.

Insert a value with add. Adding something already present simply does nothing, keeping items unique.

Because membership is unique, adding 7 twice leaves just one 7. A set dedupes for you automatically.

Test presence with the in operator. This is a set core strength: answering belongs-or-not very quickly.

Use len to see how many unique items a set holds. Duplicates never inflate this count.

Take an item out with remove. After removal the set no longer reports that value as present.

You can loop a set to visit each member, but the order is not guaranteed. Sets care about membership, not sequence.

Combine sets with union to get every item from both, still with no duplicates.

Find shared items with intersection. It keeps only the values present in both sets.

Reach for a set to remove duplicates or test membership repeatedly. It beats scanning a list every time.

You add the value 7 to an empty Set, then add 7 again. What is len of the set?

A Set stores unique items for fast membership tests. Use add and remove, in to check, and union or intersection to combine. 🎯