1641. Count Sorted Vowel Strings | LeetCode Solution

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`

class Solution {public: int countVowelStrings(int n) { vector<int>dp(5,1); int ans=0; while(--n){ for(int i=3; i>=0; i--){ dp[i]+=dp[i+1]; } } for(auto x:dp)ans+=x; return ans; }};

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`

class Solution {

public:

int countVowelStrings(int n) {

vector<int>dp(5,1);

int ans=0;

while(--n){

for(int i=3; i>=0; i--){

dp[i]+=dp[i+1];

}

}

for(auto x:dp)ans+=x;

return ans;

}

};

## 0 Comments

If you have any doubts/suggestion/any query or want to improve this article, you can comment down below and let me know. Will reply to you soon.