Checking if the user inputs the same string twice using array

Question

i want to check if the user inputs a same string twice using array. don't have any idea on what codes to use can you suggest anything?

if the user inputs "1A" twice i want to print "Already Taken", and if the user enter a string which is not in my Array(arr) i want to print "invalid input"

this is my array

      string[,] arr = new string[,]
        {
            {"1A","2A","3A","4A","5A"},
            {"1B","2B","3B","4B","5B"},
            {"1C","2C","3C","4C","5C"},
            {"1D","2D","3D","4D","5D"},
        };

You'll have to give some sample input/output, the question is not very clear — Jonesopolis
– Jonesopolis, Commented Oct 13, 2014 at 12:31
@DorCohen that really doesn't sound like a LINQ question; I genuinely have no clue what the OP is trying to do, but I'm still pretty confident that LINQ isn't the first tool to pick up — Marc Gravell
– Marc Gravell, Commented Oct 13, 2014 at 12:32
@Josh you haven't given us any context as to how the array relates to the user's input... is the question here "the user must select two different values that are in the array"?. Or is it "the array represents the user's input; the values must be distinct"? — Marc Gravell
– Marc Gravell, Commented Oct 13, 2014 at 12:33
@MarcGravell take a look on my answer, I think that's what he meant — Dor Cohen
– Dor Cohen, Commented Oct 13, 2014 at 12:34

Tim Schmelter · Accepted Answer · 2014-10-13 12:36:43Z

3

You can use a HashSet<string> to check if there are duplicates:

var set = new HashSet<string>();
bool noDuplicate = arr.Cast<string>().All(set.Add);

answered Oct 13, 2014 at 12:36

Tim Schmelter

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1 Comment

Marc Gravell Over a year ago

very tidy implementation

Dmitrii Bychenko · Accepted Answer · 2014-10-13 12:34:31Z

2

You can use Set, e.g. HashSet<String>:

  HashSet<String> hs = new HashSet<string>();

  foreach(var item in arr)
    if (!hs.Add(item)) {
      // User used "item" at least twice
      break; 
    }

answered Oct 13, 2014 at 12:34

Dmitrii Bychenko

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1 Comment

Marc Gravell Over a year ago

btw; you can simplify to just if(!hs.Add(item)) { /* fail */ } - this avoids doing a separate Contains/Add test per item.

Dor Cohen · Accepted Answer · 2014-10-13 12:33:38Z

1

You can try using LINQ, something like this:

var query = arr.GroupBy(x=>x)
              .Where(g=>g.Count()>1)
              .ToList();

answered Oct 13, 2014 at 12:33

Dor Cohen

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Comments

Thaoden · Accepted Answer · 2014-10-13 13:23:42Z

1

You can try :

  HashSet<String> hash = new HashSet<string>();

  string input = "TEST";
  bool found = false;

  foreach(string item in arr)
  {
      if (item.Equals(input))
      {
          if (hash.Contains(item))
          {
              Console.WriteLine("Already Taken");
          }
          else
          {
              hash.Add(item);
          }
          found = true;
          break;
      }
   }

  if (!found)
  {
      Console.WriteLine("Invalid Input");
  }

edited Oct 13, 2014 at 13:23

Thaoden

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answered Oct 13, 2014 at 12:43

Benji_9989

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