因为最高二次方，所以只需要分开判断即可

#include <iostream>
#include <cstdio>
#include <string>
#include <cmath>
#include <cstring>

using namespace std;

int main(){
    string str;
    int a1 = 0, b1 = 0, c1 = 0;  //左边系数
    int a2 = 0, b2 = 0, c2 = 0;  //右边系数
    while(cin >> str){
        int len = str.size();
        bool right = false;  //判断等式左右
        bool Symbol = true;  //+号为true，-号为false
        int temp = 0;
        for(int i = 0; i < len; i++){
            if(!right){  //等式左边
                if(str[i] == '='){
                    if(temp != 0){
                        c1 = temp;
                        if(!Symbol) c1 = -c1;
                        temp = 0;
                    }
                    right = true;
                    Symbol = true;
                }
                else if(isdigit(str[i])) temp = 10 * temp + str[i] - '0';
                else if(str[i] == '+' || str[i] == '-') Symbol = str[i] ...