Question

I am looking for an efficient way to detect the number of unique values in an array.

My current approach:

1. Quicksort array of integers
2. Then run a loop to compare elements.

In code:

  yearHolder := '';
  for I := 0 to  High(yearArray) do
  begin
    currYear := yearArray[i];
    if (yearHolder <> currYear) then
    begin
      yearHolder := currYear;
      Inc(uniqueYearNumber);
    end;
  end;

Answer 1

Here is an example with the THashedStringList:

hl := THashedStringList.Create; // in Inifiles
try
  hl.Sorted := True;
  hl.Duplicates := dupIgnore; // ignores attempts to add duplicates
  for i := 0 to  High(yearArray) do
    hl.Add(yearArray[i]);
  uniqueYearCount := hl.Count;
finally
  hl.Free;
end;