在Delphi中以数字方式对Tstringlist中的数字数据进行排序

编程问答 2022-05-04

问题描述

大量数字数据（来自数据库）存储在 Tstringlist 变量中。数据可能如下所示：

4
4 1/2
12.006
13 3/8
1.05
13.25
5 1/2
2.25
13 5/8

通过将 Tstringlist 的 sort 属性设置为 true，它们将按文本排序，因此 13.25 出现在 4 之前。

如何对这些数据进行数字排序（有效地）？

（德尔福，Rad Studio 10.4）

解决方法

这是一个解决方案：

// Conversion accepting input like '4','4.003','4 1/2' or '1/4'
// No leading or trailing space allowed (use trim if required).
function MyStrToFloat(const S : String) : Double;
var
    I,J : Integer;
    FS   : TFormatSettings;
begin
    I := Pos('/',S);
    if I > 0 then begin
        // We have a fractional part
        J := Pos(' ',S);
        if J > 0 then
            // Both integer and fractional parts
            Result := StrToInt(Trim(Copy(S,1,J - 1)))
        else
            Result := 0;
        Result := Result + StrToInt(Trim(Copy(S,J + 1,I - J - 1))) /
                           StrToInt(Trim(Copy(S,I + 1)));
    end
    else begin
        FS.DecimalSeparator := '.';
        Result := StrToFloat(S,FS);
    end;
end;

function StringListSortProc(
    List   : TStringList;
    Index1 : Integer;
    Index2 : Integer): Integer;
var
    N1,N2: Double;
begin
    N1 := MyStrToFloat(List[Index1]);
    N2 := MyStrToFloat(List[Index2]);
    if N1 > N2 then
        Result := 1
    else if N1 < N2 then
        Result := -1
    else
    Result := 0;
end;


procedure TForm1.Button1Click(Sender: TObject);
var
    SL : TStringList;
    S  : String;
begin
    SL := TStringList.Create;
    try
        SL.Add('4');
        SL.Add('1/2');
        SL.Add('4 1/2');
        SL.Add('12.006');
        SL.Add('13 3/8');
        SL.Add('1.05');
        SL.Add('13.25');
        SL.Add('5 1/2');
        SL.Add('2.25');
        SL.Add('13 5/8');

        Memo1.Lines.Add('Raw:');
        for S in SL do
            Memo1.Lines.Add(S);

        SL.CustomSort(StringListSortProc);

        Memo1.Lines.Add('Sorted:');
        for S in SL do
            Memo1.Lines.Add(S);
    finally
        SL.Free;
    end;
end;

转换是在排序中完成的，效率不是很高。最好用转换后的值创建一个新列表，然后对其进行排序。或者在从数据库加载列表时进行转换。你有这个想法...

,

enter image description here

两个组件可以解决您的问题：

  1. StrCmpLogical 是你的朋友。它使用自然排序 - 字符串中的数字被视为数字内容而不是文本。
  2. 这个 SO 帖子 How do I enter fractions in Delphi?

我把它放在下面：

unit Unit1;

interface

uses
  Winapi.Windows,Winapi.Messages,System.SysUtils,System.Variants,System.Classes,Vcl.Graphics,Vcl.Controls,Vcl.Forms,Vcl.Dialogs,Vcl.StdCtrls;

type

  TForm1 = class(TForm)
    Memo1: TMemo;
    ButtonSort: TButton;
    Memo2: TMemo;
    procedure ButtonSortClick(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

  //Natural sorting - Digits in the strings are considered as numerical content rather than text. This test is not case-sensitive.
  function StrCmpLogicalW(P1,P2: PWideChar): Integer;  stdcall; external 'Shlwapi.dll';
  function StrCmpLogical(const S1,S2: string): Integer;

var
  Form1: TForm1;

implementation

{$R *.dfm}

function StrCmpLogical(const S1,S2: string): Integer;
begin
  result := StrCmpLogicalW(PChar(S1),PChar(S2));
end;

function CustomNbrSort(List: TStringList; Index1,Index2: Integer): Integer;
begin
  result := StrCmpLogical(List[index1],List[index2]);
end;

procedure DoCustomSort(const List : TStringList);
begin
  List.CustomSort(CustomNbrSort);
end;

// https://stackoverflow.com/questions/18082644/how-do-i-enter-fractions-in-delphi
function FractionToFloat(const S: string): real;
var
  BarPos: integer;
  numStr,denomStr: string;
  num,denom: real;
begin
  BarPos := Pos('/',S);
  if BarPos = 0 then
    Exit(StrToFloat(S));
  numStr := Trim(Copy(S,BarPos - 1));
  denomStr := Trim(Copy(S,BarPos + 1,Length(S)));
  num := StrToFloat(numStr);
  denom := StrToFloat(denomStr);
  result := num/denom;
end;

function FullFractionToFloat(S: string): real;
var
  SpPos: integer;
  intStr: string;
  frStr: string;
  int: real;
  fr: real;
begin
  S := Trim(S);
  SpPos := Pos(' ',S);
  if SpPos = 0 then
    Exit(FractionToFloat(S));
  intStr := Trim(Copy(S,SpPos - 1));
  frStr := Trim(Copy(S,SpPos + 1,Length(S)));
  int := StrToFloat(intStr);
  fr := FractionToFloat(frStr);
  result := int + fr;
end;

procedure TForm1.ButtonSortClick(Sender: TObject);
begin
  var MyList : TStrings := TStringList.Create;
  try
    //MyList.Assign(Memo1.Lines);
    var MyFormatSettings : TFormatSettings := FormatSettings; //Make a copy of the global variable;
    MyFormatSettings.DecimalSeparator := '.'; //The system's seporator may be a comma ','

    for var i : integer := 0 to Memo1.Lines.Count - 1 do begin
      var s : string := Memo1.Lines[i];
      if not s.Contains('.') then
         s := FloatToStr(FullFractionToFloat(s),MyFormatSettings);
      MyList.AddObject(s,TObject(i));
    end;

    TStringList(MyList).CustomSort(CustomNbrSort);

    Memo2.Lines.Clear;
    for var i : integer := 0 to Memo1.Lines.Count - 1 do
        Memo2.Lines.Add(Memo1.Lines[Integer(MyList.Objects[i])]);
  finally
    MyList.Free;
  end;

end;

end.
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