c++ - 前缀括号的中缀

Question

我如何将其转换为接受括号的位置，目前您唯一可以使用的是 2 + 4 * 7。我无法弄清楚如何忽略括号，例如 (2 + 3) * 7 会读出 * + 2 3 7。有什么帮助谢谢。

#include <iostream>
#include <sstream>
#include <stack>
#include <limits>
#include <string>
using namespace std;

int priority(char a)
{
    int temp;

    if (a == '*' || a == '/' || a == '%')
       temp = 2;
    else  if (a == '+' || a == '-')
       temp = 1;
    return temp;
}

//start
int main()
{
    //declare a string called "infix"
    string infix;
    stringstream output;
    stack<char> s1, s2;

    cout << "Enter an arithmetic expression with no perenthesis: " << endl;
    getline(cin, infix);

    //this loops through backwards searching for the operators 
    for(int i = infix.length() - 1; i >= 0; i--)
    {
        //check the input against +,-,/,*,%
        if (infix[i] == '+' || infix[i] == '-' || 
            infix[i] == '*' || infix[i] == '/' || infix[i] == '%')
        {
            while(!s1.empty() && priority(s1.top()) > priority(infix[i]))
            {       
                output << s1.top();
                s2.push(s1.top());
                s1.pop();           
            }

            s1.push(infix[i]);
        }
        // I think i need to add an else if to check for parenthesis
        // not sure how
        else
        {   
            output << infix[i];
            s2.push(infix[i]);
        }
    }

    while(!s1.empty())
    {
        output << s1.top();
        s2.push(s1.top());
        s1.pop();
    }

    cout << "\nAnswer: ";

    while(!s2.empty())
    {
        cout << s2.top();
        s2.pop();
    }

    cout <<"\n\nPress enter to exit" << endl;
}

Answer 1

你正在寻找反向抛光符号

这是一个引用 - http://en.wikipedia.org/wiki/Reverse_polish_notation

您可以获得链接和阅读 Material 来实现它。

顺便说一句 - 不要在 6502 汇编器中这样做 - 这是一场噩梦!