345. Reverse Vowels of a String (Easy)

https://leetcode.com/problems/reverse-vowels-of-a-string/

Write a function that takes a string as input and reverse only the vowels of a string.

Example 1:

Input: "hello"
Output: "holle"

Input: "leetcode"
Output: "leotcede"

Note:
The vowels does not include the letter "y".

Solutions

class Solution {

    private boolean isVowel(char c) {
        List<Character> vowels = Arrays.asList(new Character[]{'a', 'e', 'i', 'o', 'u'});

        if (vowels.contains(String.valueOf(c).toLowerCase().charAt(0))) {
            return true;
        }

        return false;
    }

    private void swap(char[] cs, int x, int y) {
        char tmp = cs[x];
        cs[x] = cs[y];
        cs[y] = tmp;
    }

    public String reverseVowels(String s) {
        if (s == null || s.length() == 0) {
            return "";
        }

        int len = s.length();

        char[] chars = s.toCharArray();

        int left = 0;
        int right = len - 1;

        while(left < right) {
            while (left < len && !isVowel(s.charAt(left))) {
                left++;
            }

            while (right > 0 && !isVowel(s.charAt(right))) {
                right--;
            }

            if (left >= right) {
                break;
            }

            swap(chars, left, right);

            left++;
            right--;
        }

        String ans = "";
        for (int i = 0; i < len; i++) {
            ans += chars[i];
        }

        return ans;
    }
}

Incorrect Solutions

References