LL for Costya

LinkedList.pas

unit LinkedList;
interface
  type
    node =^ elem;
    elem = record
      entry : string;
      count : integer;
      next  : node;
    end;
    llist = node;

  procedure put(var list: llist; val: string);
  function get(var list: llist; index: integer): string;
  function remove(var list: llist; index: integer): string;
  procedure change(var list: llist; index: integer; val: string);
  procedure print(var list: llist);

implementation
  procedure print(var list: llist);
    begin
      if list^.next <> nil then
        print(list^.next);
      writeln(list^.entry);
    end;

  procedure put(var list: llist; val: string);
    var
      q, p: llist;
      counter: integer;
    begin
      new(q);
      q^.entry := val;
      q^.count := 0;
      q^.next  := nil;
      if list = nil then
        list := q
      else
        begin
          p := list;
          counter := 0;
          while p^.next <> nil do begin
            counter := counter + 1;
            p := p^.next;
          end;
          q^.count := counter;
          p^.next := q;
        end;
      end;

  function get(var list: llist; index: integer): string;
    var
      res, p: llist;
    begin
      if list = nil then
        get := 'The List is Empty'
      else
        begin
          p := list;
          res := nil;
          while p^.next <> nil do begin
            if p^.count = index then
              res := p;
            p := p^.next;
          end;
          if res = nil then
            get := 'Not Fount'
          else
            get := res^.entry;
        end;
    end;

    function remove(var list: llist; index: integer): string;
      var
        res, p, prev: llist;
      begin
        if list = nil then
          remove := 'The List is Empty'
        else
          begin
            p := list;
            res := nil;
            prev := nil;
            while p^.next <> nil do begin
              prev := p;
              if (p^.count + 1) = index then
                res := p^.next;
              p := p^.next;
            end;
            if res = nil then
              remove := 'Value Not Found'
            else
              begin
                prev^.next := res^.next;
                remove := res^.entry;
              end;
          end;
      end;

  procedure change(var list: llist; index: integer; val: string);
    var
      res, p: llist;
    begin
      if list <> nil then begin
        p := list;
        res := nil;
        while p^.next <> nil do begin
          if p^.count = index then
            res := p;
          p := p^.next;
        end;
        res^.entry := val;
      end;
    end;
end.

Main.pas

program main;
uses LinkedList;
var
  list: llist;
  l1, l2, tmp: string;
  size, line1, line2, after: integer;
  infile, output: text;
begin
  assign(infile, 'input.txt');
  reset(infile);

  size := 0;

  repeat
    readln(infile, tmp);
    size := size + 1;
    put(list, tmp);
  until Eof(infile);

  close(infile);

  write('Enter the line num for transfer: ');
  readln(line1);
  while line1 > size do begin
    write('Sorry, but you have only ', size, ' lines, enter another number: ');
    readln(line1);
  end;

  write('Enter into which line uo want to paste: ');
  readln(line2);
  while line2 > size do begin
    write('Sorry, but you have only ', size, ' lines, enter another number: ');
    readln(line2);
  end;

  write('After which symbol: ');
  readln(after);

  l1 := remove(list, line1);
  writeln('Line ', l1, '(',line1, ') removed');
  l2 := get(list, line2);
  writeln('Pasting into ', l2, '(', line2, ')');
  tmp := copy(l2, 0, after);
  tmp := tmp + l1;
  tmp := tmp + copy(l2, after + 1, length(l2) - after);
  change(list, line2, tmp);
  writeln('Line changed');

  assign(outfile, 'out.txt');
  rewrite(outfile);
  print(list);
  close(outfile);
end.