求助，本地可以过但是洛谷全是WA

#include<iostream>
#include<string>
using namespace std;
char m;//m表示运算类型
int main()
{
    int n;
    cin >> n;
    string s;
    getline(cin, s);
    for(int k = 0;k< n; k++) {
        int start = 0,flag=0;
        int num1 = 0; int num2 = 0;
        int num3 = 0;
        string res;
        getline(cin, s);
        if (s[0] == 'a' || s[0] == 'b' || s[0] == 'c') { 
            m = s[0];
            start = 2;
        }
        for (int i = start; i < s.length(); i++) {
            if (s[i] == ' ') {
                flag = i+1;
                break;
            }
            num1 = num1 * 10 + (int)s[i]-'0';
        }
        for (int i = flag; i < s.length(); i++) {
            num2 = num2 * 10 + (int)s[i]-'0';
        }
        //num1和num2以及运算类型都确定了
        res += to_string(num1);
        if (m == 'a') {
            num3 = num1 + num2;
            res += '+';
        }
        else if (m == 'b') {
            num3 = num1 - num2;
            res += '-';
        }
        else if (m == 'c') {
            num3 = num1 * num2;
            res += '*';
        }
        res += to_string(num2);
        res += '=';
        res += to_string(num3);
        cout << res << endl;
        cout << res.length() << endl;
    }
    system("pause");
    return 0;
}                                 ```