中缀表达式转后缀表达式

示例：9+(3-1)*3+10/2

#include<map>
#include<stack>
#include<queue>
#include<string>
#include<iostream>
using namespace std;

map<char, int> p;
struct Node {
    double num;
    char op;
    bool flag;
};
stack<Node> s;
queue<Node> q;
void midtoback(string str)
{
    Node temp;
    for (int i = 0; i < str.length();)
    {
        if (str[i] == '(')
        {
            temp.flag = false;
            temp.op = str[i];
            s.push(temp);
            i++;
        }
        else if (str[i] == ')')
        {
            while (!s.empty() && s.top().op != '(')
            {
                q.push(s.top());
                s.pop();
            }
            s.pop();
            i++;
        }
        else if(str[i]>='0'&&str[i]<='9')
        {
            temp.flag = true;
            temp.num = str[i] - '0';
            i++;
            while (i < str.length() && str[i] >= '0' && str[i] <= '9')
            {
                temp.num = temp.num * 10 + (str[i] - '0');
                i++;
            }
            q.push(temp);
        }
        else
        {
            temp.flag = false;
            while (!s.empty() && p[s.top().op] >= p[str[i]])
            {
                q.push(s.top());
                s.pop();
            }
            temp.op = str[i];
            s.push(temp);
            i++;
        }
    }
    while (!s.empty())
    {
        q.push(s.top());
        s.pop();
    }
}
int main()
{
    Node cur;
    string str;
    p['+'] = p['-'] = 1;
    p['*'] = p['/'] = 2;
    cin >> str;
    midtoback(str);
    while (!q.empty())
    {
        cur = q.front();
        if (cur.flag == true)
            cout << cur.num << " ";
        else
            cout << cur.op << " ";
        q.pop();
    }
    return 0;
}