泛型排序器 TComparer 转万一博客

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unit Unit1;
interface
uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls;
type
  TForm1 = class(TForm)
    Memo1: TMemo;
    Memo2: TMemo;
    Button1: TButton;
    Button2: TButton;
    Button3: TButton;
    Button4: TButton;
    Button5: TButton;
    Button6: TButton;
    Button7: TButton;
    Button8: TButton;
    Button9: TButton;
    Button10: TButton;
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure Button3Click(Sender: TObject);
    procedure Button4Click(Sender: TObject);
    procedure Button5Click(Sender: TObject);
    procedure Button6Click(Sender: TObject);
    procedure Button7Click(Sender: TObject);
    procedure Button8Click(Sender: TObject);
    procedure Button9Click(Sender: TObject);
    procedure Button10Click(Sender: TObject);
  end;

var
  Form1: TForm1;
implementation
{$R *.dfm}
uses Generics.Collections, Generics.Defaults; {必需的泛型单元}
//构建由 10 个整数组成的动态数组, 然后排序
procedure TForm1.Button1Click(Sender: TObject);
var
  arr: array of Integer;
  i: Integer;
begin
  {构建动态数组}
  Randomize;
  for i := 0 to 9 do begin
    SetLength(arr, Length(arr)+1);
    arr[i] := Random(10);
  end;

  {显示排序前}
  Memo1.Clear;
  for i := 0 to Length(arr) - 1 do Memo1.Lines.Add(IntToStr(arr[i]));

  {排序}
  TArray.Sort(arr); {它可以有 1个、2个、4个参数, 这里只用了一个参数, 其他是默认参数}

  {显示排序结果}
  Memo2.Clear;
  for i := 0 to Length(arr) - 1 do Memo2.Lines.Add(IntToStr(arr[i]));
end;

// TArray.Sort 的第二个参数是 IComparer 类型, 其默认值是: TComparer.Default
procedure TForm1.Button2Click(Sender: TObject);
var
  arr: array of Integer;
  i: Integer;
begin
  Randomize;
  for i := 0 to 9 do begin
    SetLength(arr, Length(arr)+1);
    arr[i] := Random(10);
  end;

  Memo1.Clear;
  for i := 0 to Length(arr) - 1 do Memo1.Lines.Add(IntToStr(arr[i]));

  {使用了排序器的默认值排序, 这和忽略这个参数是一样的}
  TArray.Sort(arr, TComparer.Default);
  Memo2.Clear;
  for i := 0 to Length(arr) - 1 do Memo2.Lines.Add(IntToStr(arr[i]));
end;

//同上两例, 变通了一下写法
procedure TForm1.Button3Click(Sender: TObject);
var
  arr: array of Integer;
  i: Integer;
  Comparer: IComparer;
begin
  Randomize;
  for i := 0 to 9 do begin
    SetLength(arr, Length(arr)+1);
    arr[i] := Random(10);
  end;

  Memo1.Clear;
  for i := 0 to Length(arr) - 1 do Memo1.Lines.Add(IntToStr(arr[i]));

  Comparer := TComparer.Default;
  TArray.Sort(arr, Comparer);
  Memo2.Clear;
  for i := 0 to Length(arr) - 1 do Memo2.Lines.Add(IntToStr(arr[i]));
end;

// TArray.Sort 的后面两个参数可以指定排序范围:
procedure TForm1.Button4Click(Sender: TObject);
var
  arr: array of Integer;
  i: Integer;
  Comparer: IComparer;
begin
  Randomize;
  for i := 0 to 9 do begin
    SetLength(arr, Length(arr)+1);
    arr[i] := Random(10);
  end;

  Memo1.Clear;
  for i := 0 to Length(arr) - 1 do Memo1.Lines.Add(IntToStr(arr[i]));

  Comparer := TComparer.Default;
  {这里指定从第 1 个元素开始, 只给 3 个元素排序}
  TArray.Sort(arr, Comparer, 0, 3);
  Memo2.Clear;
  for i := 0 to Length(arr) - 1 do Memo2.Lines.Add(IntToStr(arr[i]));
end;

//如果要倒排序, 可以建立自己的排序器, 下面就是先构建并实现了一个 TMyComparer, 然后调用:
type
  TMyComparer = class(TComparer)
  public
    function Compare(const Left, Right: Integer): Integer; override;
  end;

{ TMyComparer }
function TMyComparer.Compare(const Left, Right: Integer): Integer;
begin
  Result := Right - Left;
end;

procedure TForm1.Button5Click(Sender: TObject);
var
  arr: array of Integer;
  i: Integer;
  Comparer: TMyComparer;
begin
  Randomize;
  for i := 0 to 9 do begin
    SetLength(arr, Length(arr)+1);
    arr[i] := Random(10);
  end;

  Memo1.Clear;
  for i := 0 to Length(arr) - 1 do Memo1.Lines.Add(IntToStr(arr[i]));

  Comparer := TMyComparer.Create;
  TArray.Sort(arr, Comparer);
  Memo2.Clear;
  for i := 0 to Length(arr) - 1 do Memo2.Lines.Add(IntToStr(arr[i]));
  Comparer.Free;
end;


// 也可以用 TComparer.Construct 方法, 通过一个 TComparison 格式的函数构建排序器, 这样简单一些
function MyFunc1(const Left, Right: Integer): Integer;
begin
  Result := Right - Left;
end;

procedure TForm1.Button6Click(Sender: TObject);
var
  arr: array of Integer;
  i: Integer;
  Comparer: IComparer;
begin
  Randomize;
  for i := 0 to 9 do begin
    SetLength(arr, Length(arr)+1);
    arr[i] := Random(10);
  end;

  Memo1.Clear;
  for i := 0 to Length(arr) - 1 do Memo1.Lines.Add(IntToStr(arr[i]));

  Comparer := TComparer.Construct(MyFunc1);
  TArray.Sort(arr, Comparer);
  Memo2.Clear;
  for i := 0 to Length(arr) - 1 do Memo2.Lines.Add(IntToStr(arr[i]));
end;


//如果是给自定义类型的元素排序, 只能是自建排序器
type
  TPerson = record
    name: string;
    age: Word;
  end;

function MyFunc2(const Left, Right: TPerson): Integer;
begin
  Result := Left.age - Right.age;
end;

procedure TForm1.Button7Click(Sender: TObject);
var
  arr: array of TPerson;
  i: Integer;
  Comparer: IComparer;
begin
  SetLength(arr, 4);
  arr[0].name := 'AA'; arr[0].age := 22;
  arr[1].name := 'BB'; arr[1].age := 33;
  arr[2].name := 'CC'; arr[2].age := 44;
  arr[3].name := 'DD'; arr[3].age := 11;

  Memo1.Clear;
  for i := 0 to Length(arr) - 1 do
    Memo1.Lines.Add(Format('%s : %d', [arr[i].name, arr[i].age]));

  Comparer := TComparer.Construct(MyFunc2);
  TArray.Sort(arr, Comparer);
  Memo2.Clear;
  for i := 0 to Length(arr) - 1 do
    Memo2.Lines.Add(Format('%s : %d', [arr[i].name, arr[i].age]));
end;

// TStringComparer.Ordinal 是官方实现的用于 string 的排序器, 可直接使用.
//但它好像有问题(Delphi 2010 - 14.0.3513.24210), 以后的版本应该能改过来.
procedure TForm1.Button8Click(Sender: TObject);
var
  arr: array of string;
  i: Integer;
begin
  SetLength(arr, 4);
  arr[0] := '222';
  arr[1] := '111';
  arr[2] := 'bbb';
  arr[3] := 'aaa';

  Memo1.Clear;
  for i := 0 to Length(arr) - 1 do Memo1.Lines.Add(arr[i]);

  TArray.Sort(arr, TStringComparer.Ordinal);
  Memo2.Clear;
  for i := 0 to Length(arr) - 1 do Memo2.Lines.Add(arr[i]);
end;

//下面是实现字符串数组的到排序
function MyComparerFunc(const s1,s2: string): Integer;
begin
  Result := CompareText(s2, s1);
  //Result := -CompareText(s1, s2); {或者这样}
end;

procedure TForm1.Button9Click(Sender: TObject);
var
  arr: array of string;
  i: Integer;
  Comparer: IComparer;
begin
  Memo1.Clear;
  Memo1.Lines.CommaText := '11,33,22,AAA,CCC,BBB';
  SetLength(arr, Memo1.Lines.Count);
  for i := 0 to Length(arr) - 1 do arr[i] := Memo1.Lines[i];

  Comparer := TComparer.Construct(MyComparerFunc);
  TArray.Sort(arr, Comparer);

  Memo2.Clear;
  for i := 0 to Length(arr) - 1 do Memo2.Lines.Add(arr[i]);
end;

//可以把上一个程序简写为:
procedure TForm1.Button10Click(Sender: TObject);
var
  arr: array of string;
  i: Integer;
  Comparer: IComparer;
begin
  Memo1.Clear;
  Memo1.Lines.CommaText := '11,33,22,AAA,CCC,BBB';
  SetLength(arr, Memo1.Lines.Count);
  for i := 0 to Length(arr) - 1 do arr[i] := Memo1.Lines[i];

  Comparer := TComparer.Construct(
    function (const s1,s2: string): Integer
    begin
      Result := CompareText(s2, s1);
    end);
  TArray.Sort(arr, Comparer);

  Memo2.Clear;
  for i := 0 to Length(arr) - 1 do Memo2.Lines.Add(arr[i]);
end;

end.