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Formatted question description: https://leetcode.ca/all/2586.html

2586. Count the Number of Vowel Strings in Range

Description

You are given a 0-indexed array of string words and two integers left and right.

A string is called a vowel string if it starts with a vowel character and ends with a vowel character where vowel characters are 'a', 'e', 'i', 'o', and 'u'.

Return the number of vowel strings words[i] where i belongs to the inclusive range [left, right].

 

Example 1:

Input: words = ["are","amy","u"], left = 0, right = 2
Output: 2
Explanation: 
- "are" is a vowel string because it starts with 'a' and ends with 'e'.
- "amy" is not a vowel string because it does not end with a vowel.
- "u" is a vowel string because it starts with 'u' and ends with 'u'.
The number of vowel strings in the mentioned range is 2.

Example 2:

Input: words = ["hey","aeo","mu","ooo","artro"], left = 1, right = 4
Output: 3
Explanation: 
- "aeo" is a vowel string because it starts with 'a' and ends with 'o'.
- "mu" is not a vowel string because it does not start with a vowel.
- "ooo" is a vowel string because it starts with 'o' and ends with 'o'.
- "artro" is a vowel string because it starts with 'a' and ends with 'o'.
The number of vowel strings in the mentioned range is 3.

 

Constraints:

  • 1 <= words.length <= 1000
  • 1 <= words[i].length <= 10
  • words[i] consists of only lowercase English letters.
  • 0 <= left <= right < words.length

Solutions

Solution 1: Simulation

We just need to traverse the string in the interval $[left,.. right]$, and check if it starts and ends with a vowel. If so, the answer plus one.

After the traversal, return the answer.

The time complexity is $O(m)$, and the space complexity is $O(1)$. Where $m = right - left + 1$.

  • class Solution {
        public int vowelStrings(String[] words, int left, int right) {
            int ans = 0;
            for (int i = left; i <= right; ++i) {
                var w = words[i];
                if (check(w.charAt(0)) && check(w.charAt(w.length() - 1))) {
                    ++ans;
                }
            }
            return ans;
        }
        
        private boolean check(char c) {
            return c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u';
        }
    }
    
  • class Solution {
    public:
        int vowelStrings(vector<string>& words, int left, int right) {
            auto check = [](char c) -> bool {
                return c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u';  
            };
            int ans = 0;
            for (int i = left; i <= right; ++i) {
                auto w = words[i];
                ans += check(w[0]) && check(w[w.size() - 1]);
            }
            return ans;
        }
    };
    
  • class Solution:
        def vowelStrings(self, words: List[str], left: int, right: int) -> int:
            return sum(
                w[0] in 'aeiou' and w[-1] in 'aeiou' for w in words[left : right + 1]
            )
    
    
  • func vowelStrings(words []string, left int, right int) (ans int) {
    	check := func(c byte) bool {
    		return c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u'
    	}
    	for _, w := range words[left : right+1] {
    		if check(w[0]) && check(w[len(w)-1]) {
    			ans++
    		}
    	}
    	return
    }
    
  • function vowelStrings(words: string[], left: number, right: number): number {
        let ans = 0;
        const check: string[] = ['a', 'e', 'i', 'o', 'u'];
        for (let i = left; i <= right; ++i) {
            var w = words[i];
            if (check.includes(w[0]) && check.includes(w[w.length - 1])) {
                ++ans;
            }
        }
        return ans;
    }
    
    
  • impl Solution {
        pub fn vowel_strings(words: Vec<String>, left: i32, right: i32) -> i32 {
            let check = |c: u8| -> bool {
                c == b'a' || c == b'e' || c == b'i' || c == b'o' || c == b'u'
            };
    
            let mut ans = 0;
            for i in left..=right {
                let words_bytes = words[i as usize].as_bytes();
                let first_char = words_bytes[0];
                let last_char = words_bytes[words_bytes.len() - 1];
                if check(first_char) && check(last_char) {
                    ans += 1;
                }
            }
    
            ans
        }
    }
    

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