Practice Count Vowels Permutation
Read the task, work through the examples, and check your approach against the constraints. Use the original LeetCode task for coding and submissions.
Problem Statement
Count strings of length n using only a, e, i, o, and u. For each adjacent pair, an a may be followed only by e; e only by a or i; i by any vowel except i; o only by i or u; and u only by a. Return the count modulo 10^9 + 7.
Source: Count Vowels Permutation on LeetCode. Use the original task for its coding environment and submissions.
Examples
# Example 1
Input
n = 1
Output
5
# Example 2
Input
n = 2
Output
10
# Example 3
Input
n = 5
Output
68
Constraints
1 <= n <= 2 * 10^4
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