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

问题:

Anyone knows the Big O of the algorithm used in the Distinct() method, with a custom IEqualityComparer?

回答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).