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CountSortedVowelStrings.java
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CountSortedVowelStrings.java
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package dynamicprogramming;
import utils.LeetCode;
import utils.Level;
/**
* 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.
*/
/**
* Runtime: 0 ms, faster than 100.00% of Java online submissions for Count Sorted Vowel Strings.
* Memory Usage: 35.7 MB, less than 80.01% of Java online submissions for Count Sorted Vowel Strings.
*/
@LeetCode(no = 1641,
title = "Count Sorted Vowel Strings",
level = Level.MEDIUM,
url = "https://leetcode.com/problems/count-sorted-vowel-strings/")
public class CountSortedVowelStrings {
public int countVowelStrings(int n) {
int dp[][] = new int[n + 1][6];
for (int y = 1; y <= n; y++) {
for (int x = 5; x >= 1; x--) {
if (x == 5)
dp[y][x] = 1;
else
dp[y][x] = dp[y - 1][x] + dp[y][x + 1];
}
}
int sum = 0;
int result[] = dp[n];
for (int x : result) {
sum += x;
}
return sum;
}
}