杭电ACM1002，老是不能AC，一直都是Wrong Answer

Question

修改了几次，现在是在是没看出问题在哪，求指教，感激不尽。

#include<iostream>
#include<string>

using namespace std;

int main(){
    int num_case=0;
    string data1_str="",data2_str="";
    int data1_size=0,data2_size=0;
    int mark=0;
    int index=0;
    int j=0;
    int sum_rs[1001]={0},data1[1001]={0},data2[1001]={0};
    cin>>num_case;

    for (int i = 0; i < num_case; i++)
    {
        memset(data1,0,sizeof(data1));
        memset(data2,0,sizeof(data2));
        index=0;
        mark=0;
        cin>>data1_str;
        cin>>data2_str;
        data1_size=data1_str.length();
        data2_size=data2_str.length();

        for(j=0;j<data1_size;j++){
            char tmp=data1_str[data1_size-j-1];
            data1[j]=atoi(&tmp);
        }

        for(j=0;j<data2_size;j++){
            char tmp=data2_str[data2_size-j-1];
            data2[j]=atoi(&tmp);
        }
        for (j = 0; j < 1001; j++)
        {
            sum_rs[j]=data1[j]+data2[j]+mark;
            if (sum_rs[j]>=10)
            {
                sum_rs[j]%=10;
                mark=1;
            }else
            {
                mark=0;
            }
        }

        for (j =0; j < 1001; j++)
        {
            if (sum_rs[j]!=0)
            {
                index=j;
            }
        }
        cout<<"Case "<<i+1<<":"<<endl;
        cout<<data1_str<<" + "<<data2_str<<" = ";
        for (int j =index; j >=0; j--)
        {
            cout<<sum_rs[j];
        }
        cout<<endl;
        if(i!=num_case-1) cout<<endl;
    }
    return 0;
}

Answer 1

你连样例1+2都没通过，这应该是很明显的问题，把样例放入代码中走一遍就能发现了。
PS：你的代码太长了，这题貌似没这么麻烦？