How to append unique numbers to a list of strings

Question

I have this function, which works and gives the correct result:

  
  Pu         


        

Answer 1

Here's the VB version:

  <System.Runtime.CompilerServices.Extension()>
  Public Function Unique(List As List(Of String)) As List(Of String)
    ' 1. Remember the initial order
    ' 2. Group by the text
    ' 3. Label the entries in each group
    ' 4. Now reorder them by their original order
    ' 5. Remove the order value to get back to just the name
    Return List.
      Select(Function(Item, Index) New With {Item, Index}).
      GroupBy(Function(IndexedItem) IndexedItem.Item).
      SelectMany(Function(Group) Group.Select(Function(GroupItem, GroupIndex) New With {.Index = GroupItem.Index, .UniqueItem = GroupItem.Item & If(GroupIndex = 0, String.Empty, (GroupIndex + 1).ToString)})).
      OrderBy(Function(IndexedUniqueItem) IndexedUniqueItem.Index).
      Select(Function(IndexedUniqueItem) IndexedUniqueItem.UniqueItem).
      ToList()
  End Function

Answer 2

You could do it using GroupBy and if you want to preserve the original order you can create an anonymous type to include it, then group, then re-sort by the original order.

    string[] input = new[]{ "Apple", "Orange", "Apple", "Pear", "Banana", 
                            "Apple", "Apple", "Orange" };

    var result = input
        // Remember the initial order
        .Select((name, i) => new {name, i})
        .GroupBy(x => x.name)
        // Now label the entries in each group
        .SelectMany(g => g.Select((item, j) => 
            new {i = item.i, name = (j == 0 ? item.name : item.name + (j+1))}))
        // Now reorder them by their original order
        .OrderBy(x => x.i)
        // Remove the order value to get back to just the name
        .Select(x => x.name)
        .ToList();


    foreach (var r in result)
        Console.WriteLine(r);

Result

Apple
Orange
Apple2
Pear
Banana
Apple3
Apple4
Orange2