顺序查找与二分查找

unit Unit1;

interface

uses

Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,

Dialogs, StdCtrls;

type

TForm1 = class(TForm)

Button1: TButton;

Memo1: TMemo;

procedure Button1Click(Sender: TObject);

end;

var

Form1: TForm1;

implementation

{$R *.dfm}

{顺序查找函数}

function SeqSearch(List: TStringList; const str: string): Integer;

var

i: Integer;

begin

for i := 0 to List.Count - 1 do

if CompareText(List[i], str) = 0 then begin Result := i; Exit; end;

Result := -1;

end;

{二分查找函数; 二分查找只能针对有序列表}

function BinarySearch(List: TStringList; const str: string): Integer;

var

L,R,M: Integer;

CompareResult: Integer;

begin

Result := -1;

L := 0;

R := List.Count - 1;

while L <= R do

begin

M := (L + R) div 2;

CompareResult := CompareText(List[M], str);

if CompareResult < 0 then L := M + 1 else

if CompareResult > 0 then R := M - 1 else

begin

Result := M;

Exit;

end;

end;

end;

{对比测试}

procedure TForm1.Button1Click(Sender: TObject);

var

TestList: TStringList;

i: Integer;

n1,n2: Int64;

Count1,Count2: Integer;

s: string;

const

num = 1000000; {准备测试百万个数据}

begin

TestList := TStringList.Create;

for i := 0 to num-1 do TestList.Add(IntToHex(i,8)); {准备有序的测试值列表}

Memo1.Clear;

Count1 := 0;

Count2 := 0;

{搞 10 实验}

for i := 0 to 9 do

begin

{产生范围内的随机字串}

Randomize;

s := IntToHex(Random(num),8);

{顺序查找}

QueryPerformanceCounter(n1);

SeqSearch(TestList, s);

QueryPerformanceCounter(n2);

Memo1.Lines.Add(IntToStr(n2-n1)+ #9);

Count1 := Count1 + (n2-n1);

{二分查找}

QueryPerformanceCounter(n1);

BinarySearch(TestList, s);

QueryPerformanceCounter(n2);

Memo1.Lines[i] := Memo1.Lines[i] + IntToStr(n2-n1);

Count2 := Count2 + (n2-n1);

end;

Memo1.Lines.Add('----------------');

Memo1.Lines.Add('平均值:');

Memo1.Lines.Add(IntToStr(Count1 div 10)+ #9 + IntToStr(Count2 div 10));

Memo1.Lines.Add('----------------');

Memo1.Lines.Insert(0, '顺序'#9'二分');

TestList.Free;

end;

end.