README.md

2559. Count Vowel Strings in Ranges

You are given a 0-indexed array of strings words and a 2D array of integers queries.

Each query queries[i] = [li, ri] asks us to find the number of strings present in the range li to ri (both inclusive) of words that start and end with a vowel.

Return an array ans of size queries.length, where ans[i] is the answer to the ith query.

Note that the vowel letters are 'a', 'e', 'i', 'o', and 'u'.

Example 1:

Input: words = ["aba","bcb","ece","aa","e"], queries = [[0,2],[1,4],[1,1]]
Output: [2,3,0]
Explanation: The strings starting and ending with a vowel are "aba", "ece", "aa" and "e".
The answer to the query [0,2] is 2 (strings "aba" and "ece").
to query [1,4] is 3 (strings "ece", "aa", "e").
to query [1,1] is 0.
We return [2,3,0].

Example 2:

Input: words = ["a","e","i"], queries = [[0,2],[0,1],[2,2]]
Output: [3,2,1]
Explanation: Every string satisfies the conditions, so we return [3,2,1].

Constraints:

• 1 <= words.length <= 105
• 1 <= words[i].length <= 40
• words[i] consists only of lowercase English letters.
• sum(words[i].length) <= 3 * 105
• 1 <= queries.length <= 105
• 0 <= li <= ri < words.length

Solutions (Rust)

1. Solution

impl Solution {
    pub fn vowel_strings(words: Vec<String>, queries: Vec<Vec<i32>>) -> Vec<i32> {
        let mut prefix_sum = vec![0; words.len() + 1];
        let mut ret = vec![0; queries.len()];

        for i in 0..words.len() {
            prefix_sum[i + 1] = prefix_sum[i];

            if words[i].starts_with(|c| "aeiou".contains(c))
                && words[i].ends_with(|c| "aeiou".contains(c))
            {
                prefix_sum[i + 1] += 1;
            }
        }

        for i in 0..queries.len() {
            ret[i] = prefix_sum[queries[i][1] as usize + 1] - prefix_sum[queries[i][0] as usize];
        }

        ret
    }
}