Write a function that takes a list of integers and returns the sum of elements at even index minus the sum of the elements at odd index. Your algorithm should be efficient whether the list is implemented as a linked list or array list. For example, if the list is {1, 4, 6, 3, 2), then the function returns 2, which is (1 + 6 + 2) - (4 + 3) int evenodd (List list){