345. Reverse Vowels of a String

要注意大小寫, 其他就是index一般的基本轉換

class Solution {
public:
    string reverseVowels(string s) {
        if(s.size() == 0) return s;
        vector<int> vowels_index;
        unordered_set<char> table {'a', 'e', 'i', 'o', 'u', 'A', 'E', 'I', 'O', 'U'};
        for(int i = 0; i < s.size();i++){
            if(table.count(s[i])){
                vowels_index.push_back(i);
            }
        }
        int l = 0;
        int r = vowels_index.size() -1;
        while(l < r){
            char tmp = s[vowels_index[l]];
            s[vowels_index[l]] = s[vowels_index[r]];
            s[vowels_index[r]] = tmp;
            r--;
            l++;
        }
        return s;
    }
};