leetcode 345. Reverse Vowels(元音字母) of a String

Write a function that takes a string as input and reverse only the vowels(元音字母) 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".

这道题是简单题。

主要就是搞清楚元音字母是" a e i o u “这五个就好了，当然还包括它们的大写。

public String reverseVowels(String s) {StringBuilder sb=new StringBuilder(s);int frontPointer=0;int behindPointer=s.length()-1;while(frontPointer<behindPointer){while(frontPointer<s.length()&&!isVowels(sb.charAt(frontPointer))){frontPointer++;}while(behindPointer>=0&&!isVowels(sb.charAt(behindPointer))){behindPointer--;}if(frontPointer<behindPointer){char tmp=sb.charAt(frontPointer);sb.setCharAt(frontPointer, sb.charAt(behindPointer));sb.setCharAt(behindPointer, tmp);frontPointer++;behindPointer--;}}return sb.toString();}public boolean isVowels(char c){return c=='a'||c=='A'||c=='e'||c=='E'||c=='i'||c=='I'           ||c=='o'||c=='O'||c=='u'||c=='U';}

大神判断是否是元音字母是用 hashset 做的，也蛮好的。

public class Solution {    public String reverseVowels(String s) {        char[] list=s.toCharArray();        Set<Character> vowels = new HashSet<>(Arrays.asList(new Character[]{'a','e','i','o','u','A','E','I','O','U'}));        for (int i=0, j=list.length-1; i<j; ) {            if (!set.contains(list[i])) {                i++;                continue;            }            if (!set.contains(list[j])) {                j--;                continue;            }            char temp=list[i];            list[i]=list[j];            list[j]=temp;            i++;            j--;        }        return String.valueOf(list);    }}