[LeetCode] Reverse Vowels of a String

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”.

解题思路

双指针，一个往前移动，一个往后移动，找到元音字母时则交换。

实现代码

// Runtime: 12 mspublic class Solution {    private static final String STR = "aeiouAEIOU";    private static final Set<Character> VOWELS = new HashSet<Character>(STR.length());    static {        for (int i = 0; i < STR.length(); i++) {            VOWELS.add(STR.charAt(i));        }    }    public String reverseVowels(String s) {        StringBuilder sb = new StringBuilder(s);        int left = 0;        int right = sb.length() - 1;        while (left < right) {            while (left < right && !isVowels(sb.charAt(left))) {                ++left;            }            while (left < right && !isVowels(sb.charAt(right))) {                --right;            }            char temp = sb.charAt(left);            sb.setCharAt(left++, sb.charAt(right));            sb.setCharAt(right--, temp);        }        return sb.toString();    }    private boolean isVowels(char ch) {        return VOWELS.contains(ch);    }}