CODEWITHSUNDEEP
c#hashset
user3655934
user3655934

Reputation:

Remove elements from one Hashset where NOT in another Hashset?

I am aware of hashsetA.Except(hashsetB) to remove elements from hashsetA that exist in hashsetB. However, I want to remove elements from hashsetA that don't exist in hashsetB.

Currently I just copy hashsetA to a new Hashset then use ExceptWith() twice:

hashsetC = new HashSet<var>(hashsetA);
hashsetC.ExceptWith(hashsetB);
hashsetA.ExceptWith(hashsetC);

The performance of this is plenty good enough for my purposes, but I was wondering if there's a built in method to make this faster/more concise? Or am I missing an obvious way to select from the sets?

Upvotes: 1

Views: 6742

Answers (2)

Jeppe Stig Nielsen
Jeppe Stig Nielsen

Reputation: 62012

Simply use IntersectWith method.

hashsetA.IntersectWith(hashsetB);

Upvotes: 3

shay__
shay__

Reputation: 3990

res = hashsetA.Where(p=> hashsetB.Contains(p)).

Given that lookup in a Hashset is O(1), that should sum to O(n).

Upvotes: 1

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