(*//

标题:类似计算加减乘除二十四的算法

说明:参考 http://expert.csdn.net/Expert/FAQ/FAQ_Index.asp?id=422

修改:Zswang

日期:2003-03-17

支持:wjhu111@21cn.com

//*)

///////Begin Source

function SearchExpression(mNumbers: array of Integer;

 mDest: Integer): string;

const

 cPrecision = 1E-6;

var

 vNumbers: array of Extended;

 vExpressions: array of string;

 vLength: Integer;

 function fSearchExpression(mLevel: Integer): Boolean;

 var

   I, J: Integer;

   A, B: Extended;

   vExpA, vExpB: string;

 begin

   Result := True;

   if (mLevel <= 1) and (Abs(vNumbers[0] - mDest) <= cPrecision) then Exit;

   for I := 0 to mLevel - 1 do begin

     for J := I + 1 to mLevel - 1 do begin

       A := vNumbers[I];

       B := vNumbers[J];

       vNumbers[J] := vNumbers[mLevel - 1];

       vExpA := vExpressions[I];

       vExpB := vExpressions[J];

       vExpressions[J] := vExpressions[mLevel - 1];

       vExpressions[I] := '(' + vExpA + '+' + vExpB + ')';

       vNumbers[I] := A + B;

       if fSearchExpression(mLevel - 1) then Exit;

       vExpressions[I] := '(' + vExpA + '-' + vExpB + ')';

       vNumbers[I] := A - B;

       if fSearchExpression(mLevel - 1) then Exit;

       vExpressions[I] := '(' + vExpB + '-' + vExpA + ')';

       vNumbers[I] := B - A;

       if fSearchExpression(mLevel - 1) then Exit;

       vExpressions[I] := '(' + vExpA + '*' + vExpB + ')';

       vNumbers[I] := A  *  B;

       if fSearchExpression(mLevel - 1) then Exit;

       if B <> 0 then begin

         vExpressions[I] := '(' + vExpA + '/' + vExpB + ')';

         vNumbers[I]  :=  A  /  B;

         if fSearchExpression(mLevel - 1) then Exit;

       end;

       if A <> 0 then begin

         vExpressions[I] := '(' + vExpB + '/' + vExpA + ')';

         vNumbers[I] := B / A;

         if fSearchExpression(mLevel - 1) then Exit;

       end;

       vNumbers[I] := A;

       vNumbers[J] := B;

       vExpressions[I] := vExpA;

       vExpressions[J] := vExpB;

     end;

   end;

   Result := False;

 end;

var

 I: Integer;

begin

 vLength := Length(mNumbers);

 SetLength(vNumbers, vLength);

 SetLength(vExpressions, vLength);

 for I := 0 to vLength - 1 do begin

   vNumbers[I] := mNumbers[I];

   vExpressions[I] := IntToStr(mNumbers[I]);

 end;

 if fSearchExpression(vLength) then

   Result := vExpressions[0]

 else Result := '';

 vNumbers := nil;

 vExpressions := nil;

end;

///////End Source

///////Begin Demo

procedure TForm1.Button1Click(Sender: TObject);

begin

 Edit1.Text := SearchExpression([5, 5, 5, 1], 24);

end;

///////End Demo