g1201_1300.s1220_count_vowels_permutation

Class Solution

java.lang.Object

g1201_1300.s1220_count_vowels_permutation.Solution

public class Solution
extends Object

1220 - Count Vowels Permutation.

Hard

Given an integer n, your task is to count how many strings of length n can be formed under the following rules:

• Each character is a lower case vowel ('a', 'e', 'i', 'o', 'u')
• Each vowel 'a' may only be followed by an 'e'.
• Each vowel 'e' may only be followed by an 'a' or an 'i'.
• Each vowel 'i' may not be followed by another 'i'.
• Each vowel 'o' may only be followed by an 'i' or a 'u'.
• Each vowel 'u' may only be followed by an 'a'.

Since the answer may be too large, return it modulo 10^9 + 7.

Example 1:

Input: n = 1

Output: 5

Explanation: All possible strings are: “a”, “e”, “i” , “o” and “u”.

Example 2:

Input: n = 2

Output: 10

Explanation: All possible strings are: “ae”, “ea”, “ei”, “ia”, “ie”, “io”, “iu”, “oi”, “ou” and “ua”.

Example 3:

Input: n = 5

Output: 68

Constraints:

• 1 <= n <= 2 * 10^4

Constructor Summary

Constructors

Constructor and Description
Solution()

Method Summary

Modifier and Type	Method and Description
int	countVowelPermutation(int n)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Solution

public Solution()

Method Detail

countVowelPermutation

public int countVowelPermutation(int n)