LeetCode 1119. Remove Vowels from a String

原题链接在这里：https://leetcode.com/problems/remove-vowels-from-a-string/

题目：

Given a string s, remove the vowels 'a', 'e', 'i', 'o', and 'u' from it, and return the new string. 

Example 1:

Input: s = "leetcodeisacommunityforcoders"
Output: "ltcdscmmntyfrcdrs"

Example 2:

Input: s = "aeiou"
Output: "" 

Constraints:

• 1 <= s.length <= 1000
• s consists of only lowercase English letters.

题解：Check each character of string, if it is vowel, skip it. Otherwise, add it to the new string.

Time Complexity: O(n). n = s.length().

Space: O(1).

AC Java:

class Solution {
    public String removeVowels(String s) {
        if (s == null || s.length() == 0){
            return s;
        }
        
        HashSet<Character> hs = new HashSet<>(Arrays.asList('a', 'e', 'i', 'o', 'u'));
        StringBuilder sb = new StringBuilder();
        for(int i = 0; i < s.length(); i++){
            char c = s.charAt(i);
            if (hs.contains(c)){
                continue;
            }
            
            sb.append(c);    
        }
        
        return sb.toString();
    }
}