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What happens when you add a duplicate item to a Swift set?

In the Swift programming language, a set is an unordered collection that stores distinct values of the same type. When you attempt to add a duplicate item to a set, nothing happens – the set remains unchanged. The duplicate value is simply ignored.

Here’s an example:

var mySet: Set<Int> = [1, 2, 3]

print(mySet) // Output: [3, 2, 1]

// Add a duplicate item

print(mySet) // Output: [3, 2, 1]

In the example above, the duplicate “2” is ignored. The set remains unchanged with no duplicates. Sets use hashing to store and retrieve elements and their uniqueness is maintained automatically. If you try to add an item that is already in the set, it won’t cause an error or raise an exception; it will simply have no effect.