Union of Many Sets

Flatten multiple sets into one unique collection and return a sorted list.

sets union flatten sorting argument unpacking

Write a function `union_of_sets(*sets)` that accepts zero or more set objects as positional arguments. The function should return a sorted list containing every distinct element that appears in any of the given sets. The order of the returned list must be ascending according to Python's natural ordering. If no sets are provided, return an empty list. The input sets may contain mixed types (e.g., integers, strings) only if all elements are mutually comparable; otherwise behavior is undefined, but the test cases will use homogeneous types.

Constraints

Each set contains up to 1000 elements. The total number of elements across all sets does not exceed 10,000. The number of sets passed is between 0 and 100. The solution should run in O(total elements) time and O(union size) space.

Example

>>> union_of_sets({1, 2}, {2, 3})
[1, 2, 3]
>>> union_of_sets({1}, {2}, {3})
[1, 2, 3]
>>> union_of_sets()
[]
>>> union_of_sets({'a', 'b'}, {'b', 'c'})
['a', 'b', 'c']

10 points ~10 min

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Hints

You can use the set union operator or method repeatedly over all sets.

Starting with an empty set and updating it with each set works well.

After collecting all unique elements, sorted() will produce the required list.

Test Results

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