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1641. Count Sorted Vowel Strings

Given an integer n, return the number of strings of lengthnthat consist only of vowels (a, e, i, o, u) and are lexicographically sorted.

A string s is lexicographically sorted if for all valid i, s[i] is the same as or comes before s[i+1] in the alphabet.

Example 1:

Input: n = 1 Output: 5 Explanation: The 5 sorted strings that consist of vowels only are ["a","e","i","o","u"]. 

Example 2:

Input: n = 2 Output: 15 Explanation: The 15 sorted strings that consist of vowels only are ["aa","ae","ai","ao","au","ee","ei","eo","eu","ii","io","iu","oo","ou","uu"]. Note that "ea" is not a valid string since 'e' comes after 'a' in the alphabet. 

Example 3:

Input: n = 33 Output: 66045 

Constraints:

• 1 <= n <= 50

Solutions (Ruby)

1. Dynamic Programming

# @param {Integer} n# @return {Integer}defcount_vowel_strings(n)dp=[1] * 5(1...n).eachdo |_| dp[1] += dp[0]dp[2] += dp[1]dp[3] += dp[2]dp[4] += dp[3]enddp.sumend

Solutions (Rust)

1. Dynamic Programming

implSolution{pubfncount_vowel_strings(n:i32) -> i32{letmut dp = [1;5];for _ in1..n { dp[1] += dp[0]; dp[2] += dp[1]; dp[3] += dp[2]; dp[4] += dp[3];} dp.iter().sum()}}