[C++]中序轉前序

int _tmain(int argc, _TCHAR* argv[])
{
 stack sOperator, sOutput;

 char szData[128];
 sprintf(szData, "1+2+3*4+5*9-1");

 for (int i = strlen(szData) - 1; i >= 0 ; i--)
 {
  switch(szData[i])
  {
   case '+' :
    while ((!sOperator.empty()) && ((sOperator.top() == '*') || sOperator.top() == '/'))
    {
     sOutput.push(sOperator.top());
     sOperator.pop();
    }
    sOperator.push(szData[i]);
    break;

   case '-' :
    if (szData[i - 1] == '(')
    {
     sOutput.push(szData[i--]);
     sOutput.push(szData[i--]);
    }
    else
    {
     while(!sOperator.empty() && (sOperator.top() == '*' || sOperator.top() == '/'))
     {
      sOutput.push(sOperator.top());
      sOperator.pop();
     }
     sOperator.push(szData[i]);
    }

    break;

   case '*' :
   case '/' :
   case ')' :
    sOperator.push(szData[i]);

    break;
   case '(' :
    while(sOperator.top() != ')')
    {
     sOutput.push(sOperator.top());
     sOperator.pop();
    }
    sOperator.pop();

    break;
   default :
    sOutput.push(szData[i]);
    break;

  }
 }

 while (!sOperator.empty())
 {
  sOutput.push(sOperator.top());
  sOperator.pop();
 }

 while(!sOutput.empty())
 {
  printf("%c", sOutput.top());
  sOutput.pop();
 }

 printf("\r\n");

 system("pause");

 return 0;

}