LeetCode in Kotlin

1641. Count Sorted Vowel Strings

Medium

Given an integer n, return the number of strings of length n that 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

Solution

class Solution {
    fun countVowelStrings(n: Int): Int {
        if (n == 1) {
            return 5
        }
        var arr = intArrayOf(1, 1, 1, 1, 1)
        var sum = 5
        for (i in 2..n) {
            val copy = IntArray(5)
            for (j in arr.indices) {
                if (j == 0) {
                    copy[j] = sum
                } else {
                    copy[j] = copy[j - 1] - arr[j - 1]
                }
            }
            arr = copy.copyOf(5)
            sum = 0
            for (k in arr) {
                sum += k
            }
        }
        return sum
    }
}

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