编写一个程序，该程序使用链表堆栈将中缀表示法的方程转换为后缀表示法。程序的堆栈部分是自己的类，在自己的头文件中，并且实现正确（能够编译运行我教授提供的test main）。我目前正在研究将中缀字符串转换为继承类中的后缀字符串的实际函数。我有以下代码，我认为它在某处错误地完成了调车场算法，因为我得到了奇怪的输出。
template <class myType>
void infixToPostfix<myType>::convertToPostfix()
{
linkedStack<char> newS; //creating a new char stack
string output; //creating the postfix output string
for(int i = 0; i < infx.length(); i++) //cycle through the entire string
{
if (isgraph(infx[i])) //skip spaces
{
if (isalpha(infx[i])) //if the char is a letter (caps or uncaps)
{
output += infx[i]; //append it to output
}
else
{
if (newS.isEmptyStack()) newS.push(infx[i]);
else if (precedence(infx[i], newS.top()) //check if the current char has higher precedence than the top of the stack, or if the stack is empty
{
newS.push(infx[i]); //push the current char onto the stack
}
else if (infx[i] == ')') //check if the current char is a closing paren
{
for(;;)
{
if (newS.isEmptyStack()) break;
if (newS.top() != '(') //check if the top of the stack isn't an open paren
{
output += newS.top(); //append the top of the stack to the output
newS.pop(); //pop the top of the stack off
}
else //the top of the stack is a (
{
newS.pop(); //pop the ( off the stack
break; //break out of the for loop
}
}
}
else //the current char doesn't have higher precedence than the top of the stack
{
output += newS.top(); //append to the top of the stack to output
newS.pop(); //pop off the top of the stack
newS.push(infx[i]); //put the current char onto the top of the stack
}
}
}
}
while (!newS.isEmptyStack()) //not sure if this works, assuming we're at the end of the line at this point, and if there's anything on the stack we need to append it to the output
{
output += newS.top();
newS.pop();
}
pfx = output; //setting pfx to the output (pfx is the class variable for the postfix output)
}
我显示后缀字符串的功能如下
template <class myType>
void infixToPostfix<myType>::showPostfix()
{
cout << "Postfix Expression: " << pfx << endl;
}
运行程序时，我得到以下输出。
silverbox@silverbox-VirtualBox:~/Dropbox/CS202/ass13$ ./a.out testinput1.txt
Infix Expression: A + B - C
-ostfix Expression: AB+C
Infix Expression: A + B * C
*+stfix Expression: ABC
Infix Expression: A * B + C / D
/+stfix Expression: AB*CD
Infix Expression: (A + B) * C
*+(tfix Expression: AB)C
Infix Expression: A * (B + C) / D
/+(tfix Expression: A*BC)D
Infix Expression: (A + B) * (C - D)
-(+(fix Expression: AB)*CD)
Infix Expression: A * (B + C / D)
/+(tfix Expression: A*BCD)
Infix Expression: A + ((B + C) * (E - F) - G) / (H - I)
-(--(+( Expression: A+(BC)*EF)G)/HI)
silverbox@silverbox-VirtualBox:~/Dropbox/CS202/ass13$
老实说，我不明白为什么看起来像后缀表达式的奇数位会被推到我 cout 中的字符串上。任何提示/帮助？
编辑：在进行 ymett 建议的更改后，我的输出如下。我现在正试图找出我在尝试处理括号时出错的地方。
silverbox@silverbox-VirtualBox:~/Dropbox/CS202/ass13$ ./a.out testinput1.txt
Infix Expression: A + B - C
Postfix Expression: AB+C-
Infix Expression: A + B * C
Postfix Expression: ABC*+
Infix Expression: A * B + C / D
Postfix Expression: AB*CD/+
Infix Expression: (A + B) * C
Postfix Expression: AB)C*+(
Infix Expression: A * (B + C) / D
Postfix Expression: A*BC)D/+(
Infix Expression: (A + B) * (C - D)
Postfix Expression: AB)*CD)-(+(
Infix Expression: A * (B + C / D)
Postfix Expression: A*BCD)/+(
Infix Expression: A + ((B + C) * (E - F) - G) / (H - I)
Postfix Expression: A+(BC)*EF)G)/HI)-(--(+(
silverbox@silverbox-VirtualBox:~/Dropbox/CS202/ass13$