Reverse Vowels of a String

class Solution {
public:

    static bool comp(char c){
        c = tolower(c);
        return (c == 'a' || c == 'e' || c == 'o' || c == 'i' || c == 'u');
    }

    string reverseVowels(string s) {
        int l = 0, r = s.size() - 1;
        while(l < r){
            while(l < r && !comp(s[l])) l++;
            while(l < r && !comp(s[r])) r--;
            swap(s[l++], s[r--]);
        }
        return s;
    }
};