leetcode [#344]

目录

• 1. 题目
• 2. 解决方案
• 3. 注意事项

题目

Write a function that takes a string as input and reverse only the vowels of a string.

Example:
Given s = “hello”, return “holle”.
Given s = “leetcode”, return “leotcede”.

Note:
The vowels does not include the letter “y”.

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解决方案

public class Solution {
    public String reverseVowels(String s) {
        int N = s.length();
        if(s == null || N == 0) return "";
        StringBuilder builderVowel = new StringBuilder();
        for(int i = 0; i < N; i++){
            if(isVowel(s.charAt(i))){
                builderVowel.append(s.charAt(i));
            }
        }
        int k = builderVowel.length()-1;
        StringBuilder builder = new StringBuilder();
        for(int i = 0; i < N; i++){
            if(!isVowel(s.charAt(i))){
                builder.append(s.charAt(i));
            } else {
                builder.append(builderVowel.charAt(k));
                k--;
            }
        }
        return builder.toString();
    }
    private static boolean isVowel(char input){
        if('a' == input || 'e' == input || 'i' == input || 'o' == input || 'u' == input || 
                'A' == input || 'E' == input || 'I' == input || 'O' == input || 'U' == input){
            return true;
        } else {
            return false;
        }
    }
}

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注意事项

1. 元音字母为a,e,i,o,u，同时要考虑到大写。
2. 第一次遍历找到所有元音字母并按顺序保存到一个builderVowel中。第二次遍历，如果当前为不是原因，直接添加到结果builder中，如果当前位是元音字母，则从builderVowel尾部取出一个字符添加到builder中。