I have an array of Items, each one is a structure with an expiration date field (a string based on the pattern: dd/mm/yyyy).
I sorted the array with maxsort algorithm but came across a promblem when several Items had the same expiration date.
According to the exercise`s instructions, in the above-mentioned scenario the order between the Items should be by the order of their appearance in the presorted array.

Here is the code:

typedef struct _item {
    char item_name[ITEM_NAME_LENGTH];
    char department[DEPARTMENT_NAME_LENGTH];
    char expiration_date[EXPIRATION_DATE_STRING_LENGTH];
    double price;
    int available;
}Item;

void swap(Item* xp, Item* yp)
{
    Item temp = *xp;
    *xp = *yp;
    *yp = temp;
}

void Sort_By_Date(Item* store, int *len)
{
    Item* temp_store = (Item*)malloc(*(len) * sizeof * store);
    int length, i;
    for (length = *(len); length > 1; --length)
    {
        int i_max = Index_of_max(store, length);
        swap(&store[length - 1], &store[i_max]);
    }
    free(temp_store);
}

case 2:
        {
            Sort_By_Date(store, len);
            printf("You chose to sort the inventory by the expiration date.\n");
            Actions_Menu();
            continue;
        }

I thought about making a copy of the array before the sorting and then deal with the duplication problem, but couldn`t come up with the right solution.

thanks in advance!