unit Unit1 interface uses Windows Messages SysUtils Variants Classes G

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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);
private
{ Private declarations }
public
{ Public declarations }
function SubNumStrings (Str1, Str2 : string): string;
function AddNumStrings (Str1, Str2 : string): string;
function MultiplyNumStrings (Str1, Str2 : string): string;
function factorial(var n : integer) : string;
end;
var
Form1: TForm1;
implementation
{$R *.dfm}
function TForm1.AddNumStrings (Str1, Str2 : string): string;
var
i : integer;
carryStr : string;
worker : integer;
workerStr : string;
begin
Result := inttostr (length(Str1));
Result := '';
carryStr := '0';
// make numbers the same length
while length(Str1) < length(Str2) do
Str1 := '0' + Str1;
while length(Str1) > length(Str2) do
Str2 := '0' + Str2;
i := 0;
while i < length(Str1) do
begin
worker := strtoint(copy(Str1, length(str1)-i, 1)) +
strtoint(copy(Str2, length(str2)-i, 1)) +
strtoint (carryStr);
if worker > 9 then
begin
workerStr := inttostr(worker);
carryStr := copy(workerStr, 1, 1);
result := copy(workerStr, 2, 1) + result;
end
else
begin
result := inttostr(worker) + result;
carryStr := '0';
end;
inc(i);
end; { while }
if carryStr <> '0' then
result := carryStr + result;
end;
function TForm1.SubNumStrings (Str1, Str2 : string): string;
var
i : integer;
carryStr : string;
worker : integer;
workerStr : string;
begin
Result := inttostr (length(Str1));
Result := '';
carryStr := '0';
// make numbers the same length
while length(Str1) < length(Str2) do
Str1 := '0' + Str1;
while length(Str1) > length(Str2) do
Str2 := '0' + Str2;
i := 0;
while i < length(Str1) do
begin
worker := strtoint(copy(Str1, length(str1)-i, 1)) -
strtoint(copy(Str2, length(str2)-i, 1)) +
strtoint (carryStr);
if worker < 0 then
begin
workerStr := inttostr(worker + 10);
carryStr := '-1';
result := workerStr + result;
end
else
begin
result := inttostr(worker) + result;
carryStr := '0';
end;
inc(i);
end; { while }
if carryStr <> '0' then
result := carryStr + result;
end;
function TForm1.MultiplyNumStrings (Str1, Str2 : string): string;
var
i, j : integer;
carryStr : string;
worker : integer;
workerStr : string;
tempResult : string;
begin
Result := '';
carryStr := '0';
tempResult := '';
// process each digit of str1
for i := 0 to length(Str1) - 1 do
begin
while length(tempResult) < i do
tempResult := '0' + tempResult;
// process each digit of str2
for j := 0 to length(Str2) - 1 do
begin
worker := (strtoint(copy(Str1, length(str1)-i, 1)) *
strtoint(copy(Str2, length(str2)-j, 1))) +
strtoint (carryStr);
if worker > 9 then
begin
workerStr := inttostr(worker);
carryStr := copy(workerStr, 1, 1);
tempResult := copy(workerStr, 2, 1) + tempResult;
end
else
begin
tempResult := inttostr(worker) + tempResult;
carryStr := '0';
end;
end; { for }
if carryStr <> '0' then
tempResult := carryStr + tempResult;
carryStr := '0';
result := addNumStrings (tempResult, Result);
tempResult := '';
end; { for }
if carryStr <> '0' then
result := carryStr + result;
end;
function TForm1.factorial(var n : integer) : string;
var i : integer;
r : string;
begin
r := '1';
for i := 2 to n do
r := MultiplyNumStrings(r, IntToStr(i));
factorial := r;
end;
procedure TForm1.Button1Click(Sender: TObject);
var a ,b : integer;
begin
a := 70;
b := 50;
Memo1.Text := SubNumStrings( factorial(a), factorial(b)) ;
end;
end.