The Big O of Distinct() method with a Custom IEqualityComparer

Question

谁知道使用自定义IEqualityComparer的Distinct()方法中使用的算法的Big O吗？

Answer 1

There's an equal question here on SO about " What guarantees are there on the run-time complexity (Big-O) of LINQ methods? "

See this section in the answer about distinct:

Distinct, GroupBy Join, and I believe also the set-aggregation methods (Union, Intersect and Except) use hashing, so they should be close to O(N) instead of O(N²).