Problem
(a) Write a program that will do addition, subtraction, multiplication, and division for arbitrarily large integers. Each integer should be represented as a list of its digits. Since the integers are allowed to be as large as you like, linked lists will be needed to prevent the possibility of overflow. For some operations, it is useful to move backwards through the list; hence, doubly linked lists are appropriate. Multiplication and division can be done simply as repeated addition and subtraction.
(b) Rewrite multiply so that it is not based on repeated addition but on standard multiplication where the first multiplicand is multiplied with each digit of the second multiplicand and then added.
(c) Rewrite the divide operation so that it is not based on repeated subtraction but on long division. It may be necessary to write an additional function that determines if the dividend is larger than the divisor in absolute value.