Вопросы к экзамену с ответами и демо-программами на Паскале / EX17

program ex017;
uses crt;
type
	TFileText=text;

	List=^ListStr;
	ListStr=record
		Info: String;
		Next,Prev:List;
	end;
{*********************************************}
procedure AddToList(X: string; var PEndList:List);
begin
	if PEndList=nil then
	begin
		New(PEndList);
		PEndList^.Info:=X;
		PEndList^.Next:=nil;
		PEndList^.Prev:=nil;
	end
	else
	begin
		New(PEndList^.Next);
		PEndList^.Prev:=PEndList;
		PEndList:=PEndList^.Next;
		PEndList^.Info:=X;
		PEndList^.Next:=nil;
	end;
end;
{*************************************}
Function CreateLists(var q: List; max:longint):List;
var
	i:longint;
	X: string;
	Uk,ListBegin:List;
begin
	X:='';
	Uk:=nil;
	q:=nil;
	AddToList(X,Uk);
	q:=Uk;
	for i:=1 to max-1 do
	begin
		X:='';
		AddToList(X,q);
	end;
	ListBegin:=Uk;
	CreateLists:=ListBegin;
end;
{***************************************}
procedure ShowFile(f1:string; i:longint);
var
	inF: TFileText;
	Str: string;
	a:longint;
begin
assign(inF,f1);
{$I-}
reset(inF);
	if ioresult<>0 then begin write('File not found!'); exit; end;
{$I+}
	for a:=1 to i do
	begin
		readln(inF,Str);
		writeln (Str);
	end;
close(inF);
end;
{*****************************************}
function RandomFill(f1:string):longint;
var
	i:longint;
	inF: TFileText;
	s:string;
begin
randomize;
assign(inF,f1);
{$I-}
reWrite(inF);
	if ioresult<>0 then begin write('Can not create file!'); exit; end;
{$I+}
i:=1;
for i:=1 to random(10) do
begin
	s:='';
	while length(s)<=5+random(20) do
	begin
		s:=s+chr(ord('a')+random(26));
	end;
writeln(inF,s);
end;
Close(inF);
ShowFile(f1,i);
randomFill:=i;
end;
{******************************************}
procedure ex17(S1,S2: string);
var
	inF,outF: TFileText;
	ListTmp,L1,L2,LEnd: List;
	Str: string;
	i:longint;
begin
	i:=RandomFill(S1);
	ListTmp:=nil;
	assign(inF,S1);
	assign(outF,S2);
{$I-}
	reset(inF);
	if ioresult<>0 then begin write('File not found!'); exit; end;
	reWrite(outF);
	if ioresult<>0 then begin write('Can not create file!'); exit; end;
{$I+}
	if i=0 then writeln('File = Nill!');
	L1:=CreateLists(ListTmp,i);
	ListTmp:=L1;
	L2:=L1^.Next;
	while not EOF(inF) do
	begin
		readln(inF,str);
		ListTmp^.Info:=str;
		ListTmp:=L2;
		L2:=ListTmp^.Prev;
	end;
	while ListTmp=nil do
	begin
		LEnd:=L2;
		readln(inF,str);
		L2:=ListTmp;
		ListTmp:=ListTmp^.Prev;
		writeln(outF, L2^.Info);
		L2:=L2^.Prev;
	end;

	{ListTmp:=L1;
	while not EOF(inF) do
	begin
		ListTmp:=L2;
		readln(inF,str);
		ListTmp^.Info:=str;
		L2:=ListTmp^.Next;
	end;

	while ListTmp^.Next<>nil do
	begin
		str:='';
		writeln(outF,ListTmp^.Info);
		ListTmp^.Next:=ListTmp;
	end;}
writeln('****************');
ShowFile(S2,i);
close(inF);
close(outF);
end;
{******************************************}

const
	S2='ex1702.txt';
	S1='ex1701.txt' ;
begin
clrscr;
randomize;
{RandomFill(S1); }
ex17(S1,S2);
{CreateLists(5);}
end.