Question

I have two Lists, they look like this

<List> ads
[0]
Headline = "Sony Ericsson Arc silver"
[1]
Headline = "Sony Ericsson Play R800I"


<List> feedItems
[0]
Headline = "Sony Ericsson Xperia Arc Silver"
[1]
Headline = "Sony Ericsson Xperia Play R800i Black"

What is the easiest way of creating a new, third list, with the elements that match each other with at least two words? Could you accomplish this in a LINQ-way maybe?

The third list would look like this

[0]
AdHeadline = "Sony Ericsson Arc silver"
MatchingFeed  = "Sony Ericsson Xperia Arc Silver"
// etc

I’ve tried traversing the first list and used the Regex.Match class, and if I find a match I populate the third list – I’m wondering what your preferred way of doing this would be, and also how to check for min. 2+ words in the expression.

Answer 1

I’m not sure regular expressions bring anything to the party here. How about the following?

// Define a helper function to split a string into its words.
Func<string, HashSet<string>> GetWords = s =>
    new HashSet<string>(
        s.Split(new[]{' '}, StringSplitOptions.RemoveEmptyEntries)
        );

// Pair up each string with its words. Materialize the second one as
// we'll be querying it multiple times.
var aPairs = ads.Select(a => new { Full = a, Words = GetWords(a) });
var fPairs = feedItems
                 .Select(f => new { Full = f, Words = GetWords(f) })
                 .ToArray();

// For each ad, select all the feeds that match more than one word.
// Then just select the original ad and feed strings.
var result = aPairs.SelectMany(
    a => fPairs
        .Where(f => a.Words.Intersect(f.Words).Skip(1).Any())
        .Select(f => new { AdHeadline = a.Full, MatchingFeed = f.Full })
    );