C#: recursive search in two different data structures

Question

I need to perform a search in two different data structures in C#, and here's the deal: I have one name (which is a string) and I want to perform a search. I have a function called Exists which will return a bool indicating whether it exists or not.

In case it exists, I increase the name (simply adding a 1 at the end of the string), and then I need to perform the search again (via method exists) to see if an object with the new name exists.

This would go on until there's an unused name, which I could use, BUT, in case it doesn't exist, now I should perform a search another data structure which contains the objects that were deleted, and if the string is found there, then I'd have to increase the name again, and start searching since the beginning. This would all end in case there's no object with such name neither using Exists method nor in the data structure where all the deleted objects are.

How could I approach this problem?

I hope I expressed myself clearly :-)

Thanks a lot in advance!

ok, no recursion my bad, sorry, maybe passing the string as parameter by reference would be a solution? — noloman
– noloman, Commented Oct 26, 2011 at 7:37
Not so clear for me. "the objects that were deleted" => What objects? You didn't talk about deleting before. — Otiel
– Otiel, Commented Oct 26, 2011 at 7:40
@Otiel Well some objects with a certain name can be deleted, and we have to search for an existing item with a name in both the existing objects, and the deleted ones — noloman
– noloman, Commented Oct 26, 2011 at 7:46

Serge Wautier · Accepted Answer · 2011-10-26 08:20:27Z

3

string BuildNextName(string originalName)
{
  string name = originalName;
  while( Exists(name) || deletedNames.Contains(name))
  {
    name = Increment(name);
  }

  return name;
}

Or did I miss something?

Using a for loop:

string BuildNextName(string originalName)
{
  for (string name=originalName; 
       Exists(name) || deletedNames.Contains(name);
       name = Increment(name));

  return name;
}

BTW, I guess your name incrementation algorithm is more complex than simply adding 1: name, name1, name2,... Basically, if the name doesn't end in a number, you append "1". If it does, you increment that number. right?

edited Oct 26, 2011 at 8:20

answered Oct 26, 2011 at 7:41

Serge Wautier

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Comments

Haris Hasan · Accepted Answer · 2011-10-26 07:41:21Z

0

a non recursive and simple solution could be something like this ( I don't see any need of recursion in this case)

   //pseudocode

    String name;
    bool condition = true;

    while(condition)
    {
        if(ExistInFirstDataStructure(name))
        {
           //increment name
        }
        else
        {
           if(ExistInDeletedDataStructure(String name))
           {
               //increment name
           }
           else
           {
               condition = false;
           }

        }
    }


    bool ExistInFirstDataStructure(String name)
    {

    }

    bool ExistInDeletedDataStructure(String name)
    {

    }

answered Oct 26, 2011 at 7:41

Haris Hasan

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Comments

George Duckett · Accepted Answer · 2011-10-26 07:41:16Z

0

Why use a loop at all?? (I know LINQ will under the hood)

var LastUsedObjectName =
    MyObjects.Select(mo => mo.Name)
             .Union( MyDeletedObjects.Select(mo => mo.Name))
             .OrderByDescending(name => /*Function to order by integer part of name*/).First();

// Now add 1 to LastUseObjectName and use that.

answered Oct 26, 2011 at 7:41

George Duckett

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Comments

Oliver · Accepted Answer · 2011-10-26 07:41:48Z

0

How about this one:

var listOfExistingNames = new List<string> { "MyName", "MyName1", "MyName3" };
var listOfDeletedNames = new List<string> { "MyName2", "MyName5" };

int counter = 0;
string baseToFindFreePlace = "MyName";
string newName = baseToFindFreePlace;

var allNames = listOfExistingNames.Concat(listOfDeletedNames);

while (allNames.Contains(newName))
{
    counter++;
    newName = baseToFindFreePlace + counter;
}

listOfExistingNames.Add(newName);

answered Oct 26, 2011 at 7:41

Oliver

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Comments

Renatas M. · Accepted Answer · 2011-10-26 07:54:45Z

0

if you create Exists methods for both data structures, you can search with recursion like this: pseudo code:

string resultName;
void Search(string name)
{
  if(ExistsInFirstStructure(name)) //name is in first data structure
    Search(name + "1"); //add 1 and try again
  else
    if(ExistsInSecondStructure(name)) //name exists in second data structure
      Search(name + "1"); //perform search again
    else
      resultName = name; //current name wasn't found in first and second data structures - we have result
}

edited Oct 26, 2011 at 7:54

answered Oct 26, 2011 at 7:47

Renatas M.

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Comments

AryanVadera · Accepted Answer · 2024-05-28 08:17:35Z

-1

To address this issue, run a series of checks and updates until you locate a unique name that does not appear in either the main collection or the deleted items collection. Here's an organised way to accomplish this in C#:

Use the Exists method to determine whether the name exists in the main collection.
If it exists, change the name by adding a '1' and check again.
If the updated name still remains, continue the procedure until you locate a name that does not appear in the main collection.
When you come across a name that does not appear in the main collection, see whether it is in the deleted items collection.
If it still persists in the deleted items collection, change the name and restart the verification process.
Continue until you locate a name that does not appear in both collections.

example:

public string GetUniqueName(string baseName) { string currentName = baseName;

    while (true)
    {
        // Check if the current name exists in the main collection
        if (_exists(currentName))
        {
            // Modify the name by appending '1'
            currentName = IncrementName(currentName);
        }
        else
        {
            // Check if the current name exists in the deleted objects collection
            if (_deletedObjects.Contains(currentName))
            {
                // Modify the name by appending '1'
                currentName = IncrementName(currentName);
            }
            else
            {
                // Name is unique in both collections
                return currentName;
            }
        }
    }
}

private string IncrementName(string name)
{
    return name + "1";
}

answered May 28, 2024 at 8:17

AryanVadera

1

1 Comment

dbc Over a year ago

This question already has an accepted answer as well as several upvoted answers, all from 2011. Why did you add this additional answer? Your code also doesn't seem to be correct, as it calls _exists() rather than Exists() as specified in the question, and assumes that the deleted objects are strings rather than objects of the same type as the existing objects.

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