#include <bits/stdc++.h>
using namespace std;

/*
测试样例：
+ 23 34

/ + 4 2 * 3 5
*/

// 将前缀表达式转换为后缀表达式(带空格版本)

// 判断字符是否是操作符
bool isOp(string c) {
    return c == "+" || c == "-" || c == "*" || c == "/";
}

string prefixToPostfix(string s) {
    stack<string> stk;
    string c; // 子串
    vector<string> q;
    stringstream s1(s);             // 构造字符串流，处理带空格的后缀表达式
    while (s1 >> c) q.push_back(c); // 将每个子串抽取出来

    for (int i = q.size() - 1; i >= 0; i--) {
        string c = q[i];
        if (isOp(c)) {
            string a = stk.top();
            stk.pop();
            string b = stk.top();
            stk.pop();
            stk.push(a + " " + b + " " + c);
        } else
            stk.push(c); // 如果是操作数，将其转换为整数并入栈
    }
    return stk.top();
}

int main() {
    string prefix = "/ + 4 2 * 3 5"; // / + 4 2 * 3 5 --> vector<>={/ + 4 2 * 3 5}
    string postfix = prefixToPostfix(prefix);
    cout << "前缀表达式: " << prefix << endl;
    cout << "后缀表达式: " << postfix << endl;
    return 0;
}