任意输入含加减乘除乘方开方的文本数学表达式文本，自动计算结果

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#include<iostream>
#include<stdio.h>
#include<string.h>

using namespace std;

int main()
{
    double a, b, c;
    char o, o2;
    cin >> a >> o >> b >> o2 >> c;
    switch (o)
    {
        case '+':
            a = a + b;
            break;
        case '-':
            a = a - b;
            break;
        case '*':
            a = a * b;
            break;
        case '/':
            a = a / b;
            break;
        case '^':
            a = 1;
            for (int i = 0; i < b; i++) a = a * b;
            break;
        case '$':
            a = 0;
            for (int i = 0; i < b; i++) a = a + b;
            break;
        default:
            break;
    }
    switch (o2)
    {