бинарное дерево

uses crt;
type PNode = ^Node;
     Node = record
       data: char;
       left, right: PNode;
     end;
 
var Tree: PNode;
    Expr: string;
 
    function Priority ( c: char ): integer;
begin
  case ( c ) of
    '+', '-': Priority := 1;
    '*', '/': Priority := 2;
    else      Priority := 100;
  end;
end;
 
function LastOperation ( Expr: string;
                  first, last: integer): integer;
var MinPrt, i, k, prt: integer;
begin
  MinPrt := 100;
  for i:=first to last do begin
    prt := Priority ( Expr[i] );
    if prt <= MinPrt then begin
      MinPrt := prt;
      k := i;
    end;
  end;
  LastOperation := k;
end;
 
function NumberNode(c: char): PNode;
var g:pnode;
begin
  New(g);
  g^.data := c;
  g^.left := nil;
  g^.right := nil;
  numbernode:=g;
end;
 
function MakeTree ( Expr: string;
                    first, last: integer): PNode;
var h:pnode;
k: integer;
begin
 if first = last then begin
    MakeTree := NumberNode ( Expr[first] );
    Exit;
 end;
 k := LastOperation ( Expr, first, last );
 New(h);
 h^.data  := Expr[k];
 h^.left  := MakeTree ( Expr, first, k-1 );
 h^.right := MakeTree ( Expr, k+1, last );
 MakeTree:=h;
end;
 
 function CalcTree(Tree: PNode): integer;
var num1, num2: integer;
begin
  if Tree^.left = nil then begin
    CalcTree := Ord(Tree^.data) - Ord('0');
    Exit;
  end;
 num1 := CalcTree(Tree^.left);
 num2 := CalcTree(Tree^.right);
 case Tree^.data  of
   '+': CalcTree := num1+num2;
   '-': CalcTree := num1-num2;
   '*': CalcTree := num1*num2;
   '/': CalcTree := num1 div num2;
   else CalcTree := MaxInt;
 end;
end;
 
Procedure Print (Var tree: pnode);
Var i: Integer;
Begin
If tree <> Nil Then
Begin
Print(tree^.right);
Print (tree^.left);
End;
End;
 
procedure LKP(Tree: PNode);
begin
  if Tree = nil then Exit;
  LKP(Tree^.left);
  write(' ', Tree^.data);
  LKP(Tree^.right);
end;
 
 
begin
  write('Введите выражение > ');
  readln( Expr );
  Tree := MakeTree( Expr, 1, Length(Expr) );
  writeln(' = ', CalcTree(Tree) );
  LKP(tree);
  print(tree);
end.