README.md

2063. Vowels of All Substrings

Given a string word, return the sum of the number of vowels ('a', 'e', 'i', 'o', and 'u') in every substring of word.

A substring is a contiguous (non-empty) sequence of characters within a string.

Note: Due to the large constraints, the answer may not fit in a signed 32-bit integer. Please be careful during the calculations.

Example 1:

Input: word = "aba"
Output: 6
Explanation:
All possible substrings are: "a", "ab", "aba", "b", "ba", and "a".
- "b" has 0 vowels in it
- "a", "ab", "ba", and "a" have 1 vowel each
- "aba" has 2 vowels in it
Hence, the total sum of vowels = 0 + 1 + 1 + 1 + 1 + 2 = 6.

Example 2:

Input: word = "abc"
Output: 3
Explanation:
All possible substrings are: "a", "ab", "abc", "b", "bc", and "c".
- "a", "ab", and "abc" have 1 vowel each
- "b", "bc", and "c" have 0 vowels each
Hence, the total sum of vowels = 1 + 1 + 1 + 0 + 0 + 0 = 3.

Example 3:

Input: word = "ltcd"
Output: 0
Explanation: There are no vowels in any substring of "ltcd".

Constraints:

• 1 <= word.length <= 105
• word consists of lowercase English letters.

Solutions (Rust)

1. Solution

impl Solution {
    pub fn count_vowels(word: String) -> i64 {
        let word = word.as_bytes();
        let mut x = 0;
        let mut ret = 0;

        for i in 0..word.len() {
            if [b'a', b'e', b'i', b'o', b'u'].contains(&word[i]) {
                x += i as i64 + 1;
            }

            ret += x;
        }

        ret
    }
}