Count Sorted Vowel Strings

Problem

Count the strings of length n over the vowels a, e, i, o and u that are non-decreasing in alphabetical order.

The count equals the number of ways to choose n items from 5 types with repetition, which is C(n + 4, 4). Compute it with the multiplicative formula and integer division.

Hint

A non-decreasing string is determined by how many of each vowel it contains.

Test cases

case 1

in: [1]

expected: 5

case 2

in: [2]

expected: 15

case 3

in: [3]

expected: 35

case 4

in: [5]

expected: 126

case 5

in: [10]

expected: 1001

Starter codePython

def count_sorted_vowel_strings(n):
    # Your code here
    pass

5 test cases · run your code against them in the editor