Program Compress;
Const
  MaxCharType=7000;
Type
  TreeLink=^TreeNode;
  TreeNode=Record
    CharName:Char;
    Left:TreeLink;
    Right:TreeLink;
    Freqency:Word;
  end;
  CharLink=^CharNode;
  CharNode=Record
    CharName:Char;
    Next:CharLink;
  end;
  CharInfor=Record
    CharName:Char;
    CodeLink:CharLink;
  end;
  Arr=array [1..MaxCharType] of TreeLink;
  CharArr=array [1..MaxCharType] of CharInfor;
Var
  WorkArr:Arr;
  TCode:CharArr;
  FileHead,Original:string;
  p,q:TreeLink;
  code,count,TotalCharType,TempVar:word;
  infile:text;
  outfile,testfile:file;
  procedure insert (Var WorkArr:Arr;c:char;Var len:word);
  var
    j:word;
    found:boolean;
  begin
    found:=false;
    for j:=1 to len do
      if (WorkArr[j]^.CharName=c) then
      begin
        inc (WorkArr[j]^.Freqency);
        found:=true;
        exit;
      end;
    if not found then
    begin
      New (WorkArr[len+1]);
      With WorkArr[len+1]^ do
      begin
        CharName:=c;
        Freqency:=1;
        Left:=Nil;
        Right:=Nil;
      end;
      inc(len);
    end;
  end;
  procedure sort(Var WorkArr:Arr;i,j:word);
  var
    x,y,t,z:word;
    u:TreeLink;
  begin
    for x:=i to j-1 do
    begin
      t:=WorkArr[x]^.Freqency;
      z:=x;
      for y:=x+1 to j do
      begin
        if WorkArr[y]^.Freqency<t then
        begin
          t:=WorkArr[y]^.Freqency;
          z:=y;
        end;
      end;
      u:=WorkArr[z];
      WorkArr[z]:=WorkArr[x];
      WorkArr[x]:=u;
    end;
  end;
  procedure preorder(u:TreeLink;t:string;Var TotalCharType:word);
  var
    temp:word;
    TChar,v:CharLink;
  begin
    if (u<>Nil) then
    begin
      if (u^.CharName<>#0) then
      begin
        TCode[TotalCharType+1].CharName:=u^.CharName;
        temp:=1;
        New (TCode[TotalCharType+1].CodeLink);
        v:=TCode[TotalCharType+1].CodeLink;
        while temp<=length(t) do
        begin
          new (TChar);
          TChar^.CharName:=t[temp];
          TChar^.Next:=Nil;
          v^.Next:=TChar;
          v:=v^.Next;
          inc(temp);
        end;
        inc(TotalCharType);
      end
      else
      begin
        preorder(u^.Left,t+'0',TotalCharType);
        preorder(u^.Right,t+'1',TotalCharType);
      end;
    end;
  end;
  procedure fileout(Original:string;TotalCharType:word);
  var
    k,j,NumWritten:word;
    v:CharLink;
  begin
    for k:=1 to length(Original) do
    begin
      for j:=1 to TotalCharType do
      begin
        if Tcode[j].CharName=Original[k] then
        begin
          v:=TCode[j].CodeLink^.Next;
          while v<>Nil do
          begin
            code:=code+(2 shl (7-count))*(ord(v^.CharName)-48);
            inc(count);
            if count>7 then
            begin
              count:=1;
              blockwrite (outfile,code,1,NumWritten);
              code:=0;
            end;
            v:=v^.Next;
          end;
        end;
      end;
    end;
  end;
  procedure init;
  begin
    New (WorkArr[1]);
    if Paramcount<2 then
    begin
      writeln;
      writeln ('  Huffman File Convertor V1.0');
      writeln ('Usages:Huffman File1 File2 [1|2]');
      writeln ('1-To Convert File1 into File2 (Default)');
      writeln ('2-To Restore File2 from File1');
      writeln;
      halt(0);
    end;
    code:=0;
    count:=1;
    TotalCharType:=0;
    FileHead:='Huffman Tree File';
  end;
  procedure prread(Original:string);
  var
    i:word;
  begin
    i:=1;
    Repeat
      insert (WorkArr,Original[i],TempVar);
      inc(i);
    Until i>length(Original);
  end;
  procedure parse;
  var
    u:TreeLink;
    len:word;
  begin
    len:=TempVar;
    sort (WorkArr,1,len);
    while len>1 do
    begin
      New (u);
      u^.Freqency:=WorkArr[1]^.Freqency+WorkArr[2]^.Freqency;
      u^.CharName:=#0;
      u^.Left:=WorkArr[1];
      u^.Right:=WorkArr[2];
      WorkArr[1]:=u;
      WorkArr[2]:=WorkArr[len];
      dec(len);
      sort (WorkArr,1,len);
    end;
  end;
  procedure restorefile;
  var
    i:word;
  begin
    assign (outfile,Paramstr(1));
    reset (outfile,1);
    assign (infile,Paramstr(2));
    rewrite (infile);
    count:=0;
    BlockRead(outfile,Original,sizeOf(FileHead),TempVar);
    if (Original<>FileHead) then
    begin
      writeln ('File Head Error!');
      halt(0);
    end;
    BlockRead(outfile,TotalCharType,SizeOf(TotalCharType),TempVar);
    for i:=1 to TotalCharType do
    begin
      New (WorkArr[i]);
      BlockRead(outfile,WorkArr[i]^.CharName,SizeOf(WorkArr[i]^.CharName),TempVar);
      BlockRead(outfile,WorkArr[i]^.Freqency,SizeOf(WorkArr[i]^.Freqency),TempVar);
      WorkArr[i]^.Left:=Nil;
      WorkArr[i]^.Right:=Nil;
    end;
    TempVar:=TotalCharType;
    parse;
    preorder(WorkArr[1],'0',TotalCharType);
    New (q);
    q^.Left:=WorkArr[1];
    q^.Right:=WorkArr[1];
    p:=q;
    BlockRead(outfile,code,1,TotalCharType);
    repeat
      inc(count);
      if (count>7) then
      begin
        count:=1;
        BlockRead(outfile,code,1,TempVar);
      end;
      if code>=2 shl (7-count) then
      begin
        p:=p^.Right;
        code:=code-(2 shl (7-count));
      end
      else
        p:=p^.Left;
      if p^.CharName<>#0 then
      begin
      write (infile,p^.CharName);
      p:=q;
    end;
    until (TempVar=0);
    close(outfile);
    close(infile);
    halt(0);
  end;
  procedure compressfile;
  var
    i,j:word;
  begin
    assign (outfile,Paramstr(2));
    rewrite (outfile,1);
    assign (infile,Paramstr(1));
    reset (infile);
    repeat
      readln (infile,Original);
      Original:=Original+#10+#13;
      prread(Original);
    until Eof(infile);
    BlockWrite (outfile,FileHead,SizeOf(FileHead),j);
    BlockWrite (outfile,TempVar,SizeOf(TempVar),j);
    for i:=1 to TempVar do
    begin
      blockwrite (outfile,WorkArr[i]^.CharName,SizeOf(WorkArr[i]^.CharName),j);
      blockwrite (outfile,WorkArr[i]^.Freqency,SizeOf(WorkArr[i]^.Freqency),j);
    end;
    parse;
    close(infile);
    assign (infile,Paramstr(1));
    reset (infile);
    preorder(WorkArr[1],'0',TotalCharType);
    Repeat
      readln(infile,Original);
      Original:=Original+#10+#13;
      fileout(Original,TotalCharType);
    Until Eof(infile);
    blockwrite (outfile,code,1,TempVar);
    close(outfile);
    close(infile);
  end;
Begin
  init;
  if Paramstr(3)='2' then
    restorefile
  else
    compressfile;
End.