Create 345. Reverse Vowels of a String.md

345. Reverse Vowels of a String.md

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+# [345. Reverse Vowels of a String](https://leetcode.com/problems/reverse-vowels-of-a-string/description/)
+# 思路
+翻转字符串中的元音字母，即A、E、I、O、U、a、e、i、o、u。常规题  
+# C++
+```
+class Solution {
+private:
+    bool isVowel(char c){
+        if('A' <= c && c <= 'Z') c = c - 'A' + 'a';
+        if(c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u') return true;
+        return false;
+    }
+public:
+    string reverseVowels(string s) {
+        int low = 0, high = s.size() - 1;
+        while(low < high){
+            while(low < high && !isVowel(s[low])) low++;
+            while(low < high && !isVowel(s[high])) high--;
+            if(low < high) swap(s[low++], s[high--]);
+        }
+        return s;
+    }
+};
+```