Arithmetic Mean by User

/** Arithmetic Mean by User
 * Implements a linked list that stores sequencial doubles inserted during reading
 * and calculates it's arithmetic mean.
 * The reading stops when the input is not a number.
 * The function returns a double containing the value of the mean.
 *
 * Requires #include <iostream> and <cstdlib>.
 */

double Arithmetic_Mean_by_User()
{
    int n=0;
    std::string input = std::string();

    struct intList{
        double num;
        struct intList *next;
    } *head, *loop;
    head = (struct intList*)malloc(sizeof(struct intList));
    head->next = NULL;

    loop = head;
    while(1)
    {
        std::cin >> input;
        if ((input.c_str())[0] < 48 || (input.c_str())[0] > 57)
            break;
        loop->num = atof(input.c_str());
        n++;
        loop->next = (struct intList*)malloc(sizeof(struct intList));
        loop->next->next = NULL;
        loop = loop->next;
    }

    if (n == 0)
        return 0;

    double mean=0;
    while (head != NULL)
    {
        mean += head->num;
        loop = head;
        head = head->next;
        free(loop);
    }
    return mean / n;
}