Time array sorting problem?

skyhannibal

I now have an array that stores time-formatted data. I want to arrange it in a certain order so that I can find the data I want. How can I do it?

Does anyone know how to help? I appreciate it!

skyhannibal

var
  a: array [0..1024] of tdatetime;
  i: integer;
  b: tdatetime;
begin
  a [i]: = datetimepicker1.datetime; // Add multiple times

  {Sort array}

  b: = a [i]; // This is the desired result
end;

supperman

You add the time format (FormatDateTime ('YYYY-MM-DD HH: MMMM: SS', A [I])) to a TStringList, write the sorting function factors (such as ascending, descending) according to your requirements, and then Sort with CustomSort. When taking out the data, format the string as TDateTime (B [I]: = StrToDateTime (SL [I]))

supperman

function Compare (List: TStringList; Index1, Index2: Integer): Integer;
begin
  Result: = CompareText (List [Index1], List [Index2]); // Ascending
end;

procedure TFormDemo.ButtonDemoClick (Sender: TObject);
var
  A: array [0..1024] of TDateTime;
  I: Integer;
  B: TDateTime;
  SL: TStringList;
begin
  Randomize;
  SL: = TStringList.Create;
  for I: = 0 to 1024 do
  begin
    A [I]: = DateUtils.IncHour (Now, Random (24));
    SL.Add (FormatDateTime ('YYYY-MM-DD HH: MMMM: SS', A [I]));
  end;
  SL.CustomSort (@Compare);
  ListBox.Items: = SL; // Look at the result
  B: = StrToDateTime (SL [5]);
end;

supperman

Of course, you can also reassign A [I] in order after sorting

skyhannibal

Hello, I see the results of sorting!
Let me change my code to see if it works.
In fact, what I want in the end is to use another time to find the time closest to it in this array. I think it will not be difficult to find it again after sorting.

skyhannibal

Still not possible, the time data is sorted, but I can’t find the data I want!
Such:
How to find the largest number in the stringlist that is less than the specified number, you haven't used stringlist very much. !
Many thanks!

gulele007

If you want to find the time closest to the time you give, do you need to sort first? Wouldn't it be enough to just traverse once? . Of course, if your time array is fixed, and you need to search multiple times, it is still useful to sort it first.
You can use the bubbling method to sort. But when you find time, you can use the dichotomy.

gulele007

In addition, date and time are actually floating point numbers in memory. Floating point sorting should be easy.

supperman

Ha ha, you have to learn to use it. Just change the comparison factor. As follows:

const
  Point = '2016-1-6 12:00:00';


function Compare(List: TStringList; Index1, Index2: Integer): Integer;
var
  Diff1, Diff2: Double;
begin
  Diff1 := ABS(StrToDateTime(List[Index1])-StrToDateTime(Point));
  Diff2 := ABS(StrToDateTime(List[Index2])-StrToDateTime(Point));
  if Diff1> Diff2 then
    Result := 1;
  if Diff1 = Diff2 then
    Result := 0;
  if Diff1 <Diff2 then
    Result := -1;
end;

procedure TFormDemo.ButtonDemoClick(Sender: TObject);
var
  A: array[0..1024] of TDateTime;
  I: Integer;
  B: TDateTime;
  SL: TStringList;
begin
  Randomize;
  SL := TStringList.Create;
  for I := 0 to 1024 do
  begin
    A[I] := DateUtils.IncHour(Now, Random(24));
    SL.Add(FormatDateTime('YYYY-MM-DD HH:MMMM:SS', A[I]));
  end;
  SL.CustomSort(@Compare);
  ListBox.Items := SL; //Look at the result
  B := StrToDateTime(SL[0]); //The most recent time
end;

My above is the absolute value of the difference.