[2, 1, 10] --> 9 In descending order: [10, 2, 1] Sum: (10 - 2) + (2 - 1) = 8 + 1 = 9 If the array is empty or the array has only one element the result should be 0 (Nothing in Haskell, None in Rust).

def sum_of_differences(arr):
    if len(arr) <= 1:
        return 0
    arr.sort(reverse=True)
    return sum(arr[i] - arr[i + 1] for i in range(len(arr) - 1))