• 題目：反轉字串中的母音字母
• 難度：Easy
• 思路：借鑑二分查詢的思想，分別從前後進行查詢，找到母音字母，就交換
• 程式碼：

public class Solution {
    public String reverseVowels(String s) {
        if(s == null || s.equals("")){
            return s;
        }
        String vowels = "aeouiAEOUI";
        StringBuilder sb = new StringBuilder(s);
        int
 
 len = s.length();
        int left = 0;
        int right = len-1;
        while(left < right){
            char ch1 = sb.charAt(left);
            char ch2 = sb.charAt(right);
            while(left < right && vowels.indexOf(ch1) == -1){
                left++;
                ch1 = sb.charAt(left
 
);
            }
             while(left < right && vowels.indexOf(ch2) == -1){
                right--;
                ch2 = sb.charAt(right);
            }
            if(left < right){
                sb.replace(left,left+1,String.valueOf(ch2));
                sb.replace(right,right
 
+1,String.valueOf(ch1));  
            } 

            left++;
            right--;

        }
        return sb.toString();
    }
}