classSolution{public:string reverseVowels(string s){int l =0;int r = s.size()-1;unordered_set<char> st ={'a','A','E','e','i','I','O','o','U','u'};while(l < r){while(l<r &&!st.count(s[l])){++l;}while(l<r &&!st.count(s[r])){--r;}swap(s[l],s[r]);++l;--r;}return s;}};