返回整数数组中的可能性数的函数

def count_possibilities(arr):
    n = len(arr)
    if n == 0:
        return 0
    elif n == 1:
        return 1
    else:
        possibilities = [0] * n
        possibilities[0] = 1
        possibilities[1] = 1 if arr[1] != 0 and (arr[0] * 10 + arr[1]) <= 26 else 0

        for i in range(2, n):
            if arr[i] != 0:
                possibilities[i] += possibilities[i-1]
            if arr[i-1] != 0 and (arr[i-1] * 10 + arr[i]) <= 26:
                possibilities[i] += possibilities[i-2]

        return possibilities[n-1]