后缀表示法的插图不尊重第二组括号

难以获得正确的结果infix ：（ a b）/（c-d）后缀：ab cd-/

我继续获得后缀：ab c/d -

我确实知道问题来自于它在推动之前无法从堆栈中弹出最后一个操作员的问题"。我做错了什么？还有其他方法可以解决这个问题吗？

#include <iostream>
#include <stack>
#include <sstream>
#include <string>
using namespace std;
int precedence(char x) {
    int op;
    if (x == '(' || x==')')
        op = 1;
    else if (x == '^')
        op = 2;
    else  if (x == '*')
        op = 3;
    else  if ( x == '/')
        op = 4;
    else  if (x == '+')
        op = 5;
    else  if (x == '-')
        op = 6;
    return op;
}
int main() 
{
    string getInfix;
    cout << "Infix: ";
    getline(cin, getInfix);
    stack<char> opStack;
    stringstream showInfix;

    for (unsigned i = 0; i < getInfix.length(); i++) 
    {
        if (getInfix[i] == '+' || getInfix[i] == '-' || getInfix[i] == '*' || getInfix[i] == '/'  || getInfix[i] == '^') 
        {
            while (!opStack.empty() && precedence(opStack.top() <= precedence(getInfix[i])) 
            {
                showInfix << opStack.top();
                opStack.pop();
            }
            opStack.push(getInfix[i]);
        }
        else if (getInfix[i] == '(') 
        {
            opStack.push(getInfix[i]);
            opStack.pop();
            if (getInfix[i]=='(' && !opStack.empty()) 
            {
                opStack.push(getInfix[i]);
                opStack.pop();
            }
        }        
        else if (getInfix [i]==')') 
        {                   
          showInfix << opStack.top();
          opStack.pop();
        }
        else 
        {
            showInfix << getInfix[i];
        }
    }
    while (!opStack.empty()) 
    {
        showInfix << opStack.top();
        opStack.pop();
    }
    cout << "Postfix: "<<""<<showInfix.str() << endl;
    cin.ignore ( numeric_limits< streamsize >:: max(),'n');
    return 0;
}