# 345.Reverse Vowels of a String

**345.Reverse Vowels of a String**

难度:Easy

> 编写一个函数，以字符串作为输入，反转该字符串中的元音字母。

```
示例 1:

输入: "hello"
输出: "holle"
示例 2:

输入: "leetcode"
输出: "leotcede"
说明:
元音字母不包含字母"y"。
```

先用一个数组保存元音字符的下标号，然后遇到元音字符的时候，反转即可。

```
class Solution {
set<char> vowels={'a','e','i','o','u','A','E','I','O','U'};
public:
    string reverseVowels(string s) {
        string res;
        // cout<<s.length()<<endl;
         if(!s.length()) return res;
        vector<int>indexs;
        for(int i=0;i<s.length();i++)
        {
            if(vowels.count(s[i])) indexs.push_back(i);
        }
        if(indexs.empty()) return s;
        // for(auto c:indexs)
        //     cout<<c<<" ";
        int start=0;
        for(int i=0;i<s.length();i++)
        {
            if(start <indexs.size() &&i==indexs[start]   )
            {
                res+=s[indexs[indexs.size()-1-start]];
                ++start;
            //    cout<<res<<endl;
            }
            else 
            {
                res+=s[i];
        //        cout<<res<<" -  "<<endl;
            }
            
        }
        return res;
    }
};
```

> 执行用时 :20ms, 在所有 C++ 提交中击败了54.85%的用户\
> 内存消耗 :11.4MB, 在所有 C++ 提交中击败了5.12%的用户


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