P1055 #4和#7WA求助

求教大佬帮忙看下哪里有问题啊＞﹏＜

C++ 14(GCC 9):

#include<iostream>
using namespace std;
int main()
{
    char a[13];
    int arr[10];
    for (int i = 0; i < 13; i++)
    {
        cin >> a[i];
    }

    int j = 0;
    for (int i = 0; i < 13; i++)
    {
        if (i == 1 || i == 5 || i == 11)
        {
            continue;
        }
        else
        {
            arr[j] = a[i] - '0';  // arr 里存的是ISBN里的数字（不包括"-"）
            j++;
        }
    }

    int len = 0;
    int x = 1;
    for (int i = 0; i < 9; i++)
    {
        len = len + arr[i] * x;
        x++;
    }
    len = len % 11;

    if (arr[9] == len)
    {
        cout << "Right";
    }
    else
    {
        arr[9] = len;

        cout << arr[0] << "-";
        for (int i = 1; i < 4; i++)
        {
            cout << arr[i];
        }
        cout << "-";

        for (int i = 4; i < 9; i++)
        {
            cout << arr[i];
        }
        cout << "-";

        if (arr[9] == 10)
        {
            cout << "X";
        }
        else
        {
            cout << arr[9];
        }
    }

    return 0;
}