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原题链接在这里：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".
Note:
The vowels does not include the letter "y".
题解：
典型的two pointers, 到了vowel时对调.
Time Complexity: O(s.length()). Space:O(s.length()), 因为建立了char array.
AC Java:
1 public class Solution { 2 public String reverseVowels(String s) { 3 HashSet<Character> hs = new HashSet<Character>(); 4 hs.add(‘A‘); 5 hs.add(‘a‘); 6 hs.add(‘E‘); 7 hs.add(‘e‘); 8 hs.add(‘I‘); 9 hs.add(‘i‘); 10 hs.add(‘O‘); 11 hs.add(‘o‘); 12 hs.add(‘U‘); 13 hs.add(‘u‘); 14 15 char [] charArr = s.toCharArray(); 16 int i = 0; 17 int j = charArr.length-1; 18 while(i<j){ 19 while(i<j && !hs.contains(charArr[i])){ 20 i++; 21 } 22 while(i<j && !hs.contains(charArr[j])){ 23 j--; 24 } 25 if(i<j){ 26 swap(charArr, i, j); 27 i++; 28 j--; 29 } 30 } 31 32 return new String(charArr); 33 } 34 35 private void swap(char [] arr, int i, int j){ 36 char temp = arr[i]; 37 arr[i] = arr[j]; 38 arr[j] = temp; 39 } 40 }
LeetCode Reverse Vowels of a String
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原文地址：http://www.cnblogs.com/Dylan-Java-NYC/p/5812211.html
