【Leetcode】Reverse Vowels of a String

题目链接：https://leetcode.com/problems/reverse-vowels-of-a-string/

题目：

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".

思路：

easy

算法：

public String reverseVowels(String s) {
       char c[] = s.toCharArray();
       Set<String> vowels = new HashSet<String>();
       vowels.add("a");
       vowels.add("e");
       vowels.add("i");
       vowels.add("o");
       vowels.add("u");
       vowels.add("A");
       vowels.add("E");
       vowels.add("I");
       vowels.add("O");
       vowels.add("U");
       int v1=-1,v2=-1;
       for(int start=0,end=c.length-1;start<end;){
        if(v1==-1){
            if(vowels.contains(c[start]+""))
                v1 = start;
            else
                start++;
        }
        if(v2==-1){
            if(vowels.contains(c[end]+""))
                v2 = end;
            else
                end--;
        }  

        if(v1!=-1&&v2!=-1){
            char tmp = c[v1];
            c[v1] = c[v2];
            c[v2] = tmp;
            v1 = -1;
            v2 = -1;
            start++;
            end--;
        }  

       }  

       return new String(c);
   }