Leetcode: Reverse Vowels of a String

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

Example 1:
Given s = "hello", return "holle".

Example 2:
Given s = "leetcode", return "leotcede".

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

Two Pointers 解法， 注意大小写

public class Solution {
    public String reverseVowels(String s) {
        StringBuffer res = new StringBuffer(s);
        int l=0, r=s.length()-1;
        while (l < r) {
            while (l<r && !isVowel(res.charAt(l))) l++;
            while (l<r && !isVowel(res.charAt(r))) r--;
            if (l == r) break;
            char temp = res.charAt(l);
            res.setCharAt(l, res.charAt(r));
            res.setCharAt(r, temp);
            l++;
            r--;
        }
        return res.toString();
    }
    
    public boolean isVowel(char c) {
        if (c=='a' || c=='e' || c=='i' || c=='o' || c=='u'|| c=='A' || c=='E' || c=='I' || c=='O' || c=='U') return true;
        else return false;
    }
}