Compare two hashsets?

Question

I have two hashsets like this:

HashSet<string> log1 = new HashSet<string>(File.ReadLines("log1.txt"));
HashSet<string> log2 = searcher(term);

How would I compare the two?

I want to make sure that log2 does not contain any entries from log1. In other words, I want to remove all(if any), items that log1 has inside log2.

Step through each element in log1 and compare them to each of the elements in log2, that's how I would do it. Although I'm not sure how you would access individual elements. I'm guessing you might be able to construct a foreach (string s in log1) for it? Note: I've never used the HashSet type, and I'm guessing — Jamie Taylor, May 17 '12 at 12:44

score 15 · Accepted Answer · answered May 17 '12 at 12:44

To remove all items from log2 that are in log1, you can use the HashSet<T>.ExceptWith Method:

log2.ExceptWith(log1);

Alternatively, you can create a new HashSet<T> without modifying the two original sets using the Enumerable.Except Extension Method:

HashSet<string> log3 = new HashSet<string>(log2.Except(log1));

score 7 · Answer 2 · answered May 17 '12 at 12:44

7

Using LINQ:

log1.Intersect(log2).Any()

See Intersect and Except on MSDN.

answered May 17 '12 at 12:44

Oded

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@RoyiNamir - `Any()` is better. – Oded May 17 '12 at 12:47
@RoyiNamir If you need to check if there are any coins in a jar youdont have to count, rather you check if there exist any? – Sandeep May 17 '12 at 13:05

score 1 · Answer 3 · edited May 17 '12 at 12:50

1

Have you seen the ExceptWith function?

Removes all elements in the specified collection from the current HashSet object.

edited May 17 '12 at 12:50

bdukes

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answered May 17 '12 at 12:44

Daniel A. White

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Compare two hashsets?

3 Answers3

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