[Leetcode] Reverse Vowels of a String, Solution

Write a function that takes a string as input and reverse only the vowels of a string.

Example 1:
Given s = "hello", return "holle".

Example 2:
Given s = "leetcode", return "leotcede".

Note:
The vowels does not include the letter "y".

[Thoughts]
双指针扫描。一个从头部，一个从尾部，发现vowel就swap。

[Code]

1:    string reverseVowels(string s) {  
2:      set<char> vowels{'a', 'o', 'e', 'i', 'u', 'A', 'O', 'E', 'I', 'U'};  
3:        
4:      for(int i =0, j = s.size()-1; i< j; ) {  
5:        if(vowels.find(s[i]) == vowels.end()) {  
6:          i++;   
7:          continue;  
8:        }  
9:          
10:        if(vowels.find(s[j]) == vowels.end()) {  
11:          j--;  
12:          continue;  
13:        }  
14:          
15:        swap(s[i], s[j]);  
16:        i++;  
17:        j--;  
18:      }  
19:        
20:      return s;  
21:    }