How to test that all items of list a are in list b

Question

I have an array of search terms, and a setence. I need to test that the sentence contains all the search terms:

var searchTerms = "fox jumped".Split(' '); var sentence = "the quick brown fox jumped over the lazy dog".Split(' '); var test = sentence.Contains(searchTerms);

I exptected test to be True -- howerver I get a compile error: 'string[]' does not contain a definition for 'Contains' and the best extension method overload 'System.Linq.Queryable.Contains(System.Linq.IQueryable, TSource)' has some invalid arguments

How should I test that sentence contains all the search terms?

SLaks · Accepted Answer · 2011-02-11 15:04:40Z

3

You're trying to check whether there are any search terms that don't appear in the sentence:

if (!searchTerms.Except(sentence, StringComparer.CurrentCultureIgnoreCase).Any())

edited Feb 11, 2011 at 15:04

answered Feb 11, 2011 at 14:57

SLaks

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5 Comments

jbehren Over a year ago

Would searchTerms.Any(term => !sentence.Contains(term)) perform faster, or would they both compile to the same IL? (Gotta love IEnumerable)

SLaks Over a year ago

@jbehren: That's much slower. It's O(n²), since it needs to loop over the other list every time.

jbehren Over a year ago

It seems that .Except follows the same behavior pattern, except that it slims the lists down to distinct values first (which means it's iterating the lists MORE than the .Any method): hookedonlinq.com/ExceptOperator.ashx Basically, creating the set difference seems like it's going to follow the same path. (I say "seems" because I don't know the inner workings of LINQ)

SLaks Over a year ago

@jbehren: Wrong. Except builds a HashSet, and is thus O(n).

jbehren Over a year ago

That makes sense then. Thanks for taking the time :)

Doctor Jones · Accepted Answer · 2011-02-11 14:59:51Z

You could do this:

//test if all of the terms are in the sentence searchTerms.All(term => sentence.Contains(term));

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