31. 中序轉後序

void get_fix(String x, int flag)

{ String a = pop(2);

     a = (flag == 1) ? x+pop(2)+a : pop(2)+a+x;

     push(2, a) ;

}

boolean IsOperand(String s)

{ if (   (s!="+") && (s!="-") && (s!="*") && (s!="/")

   && (s!="(") && (s!=")")  && (s!="&") && (s!="|")

   && (s!="^") ) return true;

  return false;

}

String postfixTOprefix(String postfix)

{  int n = postfix.Length();

   int i;

 String s, x;

     for (i=1; i<=n; i++)

     {   s = postfix[i];

         if ( IsOperand(s) ) push(2, s);

         else get_fix(s, 1);

     }

     return pop(2);

}

String postfixTOinfix(String postfix)

{  int n = postfix.Length();

   int i;

 String s, s1, s2, x, y, prev = "#";

    for (i=1; i<=n; i++)

    {   s = postfix[i];

        if (IsOperand(s))

        { push(2, s);

          push(1, "#");

        }

        else {  s1 = pop(1);

                s2 = pop(1);

                x  = pop(2);

                y  = pop(2);

                if (p(s) > p(s1) && x.Length() > 1) x = "("+x+")";

                if (p(s) > p(s2) && y.Length() > 1) y = "("+y+")";

                if (Form1->CheckBox1->Checked)

                    Form1->Memo1->Lines->Add("p("+s+")="+IntToStr(p(s))+"("+s1+")="+

                    IntToStr(p(s1))+"  p("+s2+")="+IntToStr(p(s2))+"  s1="+s1+"  s2="+

                    s2+"  x="+x+"  y="+y);

                push(2, y+s+x);

                push(1, s);

             }

     }

     while (top != -1) x = pop(1);

     return pop(2);

}

String prefixTOpostfix_reverse(String prefix)

{  int n = prefix.Length();

   int i, counter = 0;

 String s, post;

     for (i=n; i>=1; i--)

     {  s = prefix[i];

        if ( IsOperand(s) )

           push(2, s);

        else {  post = pop(2);

                post += pop(2)+s;

                if (Form1->CheckBox2->Checked) Form1->Memo1->Lines->Add(post);

                push (2, post);

             }

     }

     return pop(2);

}

String transformation(String infix, int flag)

{ int n = infix.Length();

  int i, j;

  String s, x;

     push(1, "#");

     for (i=1; i<=n; i++)

     {  s = infix[i];

        if ( IsOperand(s) ) push(2, s);

        else if (s == ")")  //將堆疊中第一個 ( 之前的運算子皆pop出並印出之

                 while ((x=pop(1))!="(") get_fix(x, flag);

             else

             {     while ( p(s) <= q(Stack[top]) )

                   {    x = pop(1);

                        get_fix(x, flag);

                    }

                    push(1, s);

             }

     }

     while (Stack[top]!= "#")

     { x = pop(1);

       get_fix(x, flag);

     }

     pop(1);

     return pop(2);

}

//---------------------------------------------------------------------------

void __fastcall TForm1::Button1Click(TObject *Sender)

{

 String infix = Edit1->Text;

 String prefix = transformation(infix, 1);

 Edit4->Text = prefix;

 Memo1->Lines->Add("infix:   "+infix);

 Memo1->Lines->Add("prefix:  "+prefix);

}

//---------------------------------------------------------------------------

void __fastcall TForm1::Button2Click(TObject *Sender)

{

 String infix = Edit1->Text;

 String postfix = transformation(infix, 2);

 Edit5->Text = postfix;

 Memo1->Lines->Add("infix:   "+infix);

 Memo1->Lines->Add("postfix: "+postfix);

}

//---------------------------------------------------------------------------

void __fastcall TForm1::Button3Click(TObject *Sender)

{

 String prefix;

 String postfix = Edit2->Text;

 Memo1->Lines->Add("postfix: "+postfix);

 prefix = postfixTOprefix(postfix);

 Edit6->Text = prefix;

 Memo1->Lines->Add("prefix:  "+prefix);

}

//---------------------------------------------------------------------------

void __fastcall TForm1::Button4Click(TObject *Sender)

{

 String postfix;

 String prefix = Edit3->Text;

 Memo1->Lines->Add("prefix:  "+prefix);

 postfix = prefixTOpostfix(prefix);

 Memo1->Lines->Add("postfix: "+postfix);

}

//---------------------------------------------------------------------------

void __fastcall TForm1::Button5Click(TObject *Sender)

{

 String postfix;

 String prefix = Edit3->Text;

 Memo1->Lines->Add("prefix:  "+prefix);

 postfix = prefixTOpostfix_reverse(prefix);

 Edit8->Text = postfix;

 Memo1->Lines->Add("postfix: "+postfix);

}

//---------------------------------------------------------------------------

void __fastcall TForm1::Button6Click(TObject *Sender)

{

 String infix;

 String postfix = Edit2->Text;

 Memo1->Lines->Add("postfix: "+postfix);

 infix = postfixTOinfix(postfix);

 Edit7->Text = infix;

 Memo1->Lines->Add("infix:   "+infix);

}

//---------------------------------------------------------------------------

void __fastcall TForm1::ListBox1Click(TObject *Sender)

{

 Edit1->Text = ListBox1->Items->operator [](ListBox1->ItemIndex);

}

//---------------------------------------------------------------------------

void __fastcall TForm1::ComboBox1Click(TObject *Sender)

{

 Edit1->Text = ComboBox1->Items->Strings[ComboBox1->ItemIndex]; ;

   //ComboBox1->Items->operator [](ComboBox1->ItemIndex);

}

//---------------------------------------------------------------------------