表达式转换

算术表达式有前缀表示法、中缀表示法和后缀表示法等形式。日常使用的算术表达式是采用中缀表示法，即二元运算符位于两个运算数中间。请设计程序将中缀表达式转换为后缀表达式。

#include <iostream>
#include<stack>
#include<map>
using namespace std;
const int maxn = 1e4 + 10;
typedef long long ll;
stack<char> s;

int main() {
    map<char, int> mp;
    string str;
    cin >> str;
    bool test = true;
    mp['-'] = 1, mp['+'] = 1;
    mp['*'] = 2, mp['/'] = 2;
    mp['('] = 3, mp[')'] = 3;
    for (int i = 0; i < str.size(); i++)
    {
        if (((i == 0 || str[i - 1] == '(') && (str[i] == '+' || str[i] == '-')) || (str[i] >= '0' && str[i] <= '9') || (str[i] == '.'))       
        {
            if (!test)         //正常
            {
                cout << " ";
            }
            if (str[i] != '+')
            {
                cout << str[i];
            }
            while (str[i + 1] == '.' || (str[i + 1] >= '0' && str[i + 1] <= '9'))
            {
                i++;
                cout << str[i];
            }
            test = false;
        }
        else {
            if (str[i] == ')')
            {
                while (!s.empty() && s.top() != '(')
                {
                    cout << ' ' << s.top();
                    s.pop();
                }
                s.pop();
            }
            else if (s.empty() || mp[str[i]] > mp[s.top()])
            {
                s.push(str[i]);
            }
            else {
                while (!s.empty() && s.top() != '(')

                {
                    cout << ' ' << s.top();
                    s.pop();
                }
                s.push(str[i]);
            }
        }
    }
    while (!s.empty()) 
    {
        cout << ' ' << s.top();
        s.pop();
    }
    return 0;
}