Remove duplicates in multi-element string[] array?

Question

I have a string[] array that is split by \r. Each row in the array has title|address in it, but every so often I end up with a duplicate of the address portion of it, which I don't want.

This:

Title1 | Address1 //[0]
Title2 | Address2 //[1]
Title3 | Address1 //[2]
Title4 | Address3 //[3]

Would become:

Title1 | Address1 //[0]
Title2 | Address2 //[1]
Title4 | Address3 //[2]

The array declaration is as follows: string[] resultsArray = results.Split('\r'); //Title|Address I then later split the row when I grab the individual elements by |.

Usage (extremely simplified):

foreach (string result in resultsArray)
{
    string splitResult[] = result.Split('|');
    title = splitResult[0];
    address = splitResult[1];
}

So if there is a duplicate address, you want to remove the title aswell? Have you tried using a Dictionary<string,string> instead? — The Scrum Meister
– The Scrum Meister, Commented Feb 14, 2011 at 21:29
@The Scrum Meister Oh, Thanks, I should have looked at it better. — nickmoriarty
– nickmoriarty, Commented Feb 14, 2011 at 21:31

Wes P · Accepted Answer · 2011-02-14 21:31:00Z

5

I'm assuming the question is, how do you prevent duplicate addresses from being entered into the list. Could you use a Dictionary?

Dictionary<string, string> addresses = new Dictionary<string, string>();

foreach(string result in resultsArray)
{
    string splitResult[] = result.Split('|');

    // check to see if address already exists, if it does, skip it.
    if(!addresses.ContainsKey(splitResult[1]))
    {
        addresses.add(splitResult[1], splitResult[0]);
    }
}

answered Feb 14, 2011 at 21:31

Wes P

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2 Comments

Sootah Over a year ago

Yes, your interpretation is a better one than my own. I ended up using: if (!resultsList.Exists(delegate(ResultsList r) { return r.title == splitResult[0]; }))

Sootah Over a year ago

As I've been loading the results into a comprehensive list with other elements.

LukLed · Accepted Answer · 2011-02-14 21:34:18Z

3

string[] strings = { "Title1 | Address1", "Title2 | Address2", "Title3 | Address1", "Title4 | Address3" };
var _strings = strings.GroupBy(s => s.Split('|')[1]).Select(g => g.Min(s => s));

answered Feb 14, 2011 at 21:34

LukLed

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Comments

Jeffrey Hantin · Accepted Answer · 2011-02-15 07:15:23Z

2

var seenItBefore = new HashSet<string>();
foreach (string result in resultsArray)
{
    string splitResult[] = result.Split('|');
    title = splitResult[0];
    address = splitResult[1];

    if (!seenItBefore.Add(address)) continue;

    // process
}

You could also supply a projecting IEqualityComparer<string[]>to Distinct() if you're building up a vine of IEnumerable<>, but since your sample doesn't use it, I decided to stick with classic procedural.

edited Feb 15, 2011 at 7:15

answered Feb 14, 2011 at 21:31

Jeffrey Hantin

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2 Comments

LukeH Over a year ago

The Add method returns a bool to indicate whether the item was already in the set, so you could just use if (!seenItBefore.Add(address)) { /* process */ } instead of the Contains/Add combo.

Jeffrey Hantin Over a year ago

@LukeH I think you got the condition inverted, since Add returns true if the add succeeds. Incorporating the change, though.

Jeff Mercado · Accepted Answer · 2011-02-14 21:36:51Z

1

Using John Skeet's ProjectionComparer, it becomes rather easy:

var comparer = new ProjectionComparer((string input) => input.Split('|')[1]);
var results = resultsArray.Distinct(comparer);

answered Feb 14, 2011 at 21:36

Jeff Mercado

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Comments

xanatos · Accepted Answer · 2011-02-14 21:58:59Z

0

Try something like:

resultArray.Select(p => p.Split('|')).Select(p => new { Name = p[0], Address = p[1] }).GroupBy(p => p.Address).Select(p => p.First()).ToArray();

edited Feb 14, 2011 at 21:58

answered Feb 14, 2011 at 21:34

xanatos

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