README_EN.md

345. Reverse Vowels of a String

中文文档

Description

Given a string s, reverse only all the vowels in the string and return it.

The vowels are 'a', 'e', 'i', 'o', and 'u', and they can appear in both cases.

 

Example 1:

Input: s = "hello"
Output: "holle"

Example 2:

Input: s = "leetcode"
Output: "leotcede"

 

Constraints:

• 1 <= s.length <= 3 * 105
• s consist of printable ASCII characters.

Solutions

Python3

class Solution:
    def reverseVowels(self, s: str) -> str:
        vowels = {'a', 'e', 'i', 'o', 'u', 'A', 'E', 'I', 'O', 'U'}
        i, j = 0, len(s) - 1
        chars = list(s)
        while i < j:
            if chars[i] not in vowels:
                i += 1
                continue
            if chars[j] not in vowels:
                j -= 1
                continue
            chars[i], chars[j] = chars[j], chars[i]
            i += 1
            j -= 1
        return ''.join(chars)

Java

class Solution {
    public String reverseVowels(String s) {
        Set<Character> vowels = new HashSet<>(Arrays.asList('a', 'e', 'i', 'o', 'u', 'A', 'E', 'I', 'O', 'U'));
        int i = 0, j = s.length() - 1;
        char[] chars = s.toCharArray();
        while (i < j) {
            if (!vowels.contains(chars[i])) {
                ++i;
                continue;
            }
            if (!vowels.contains(chars[j])) {
                --j;
                continue;
            }
            char t = chars[i];
            chars[i] = chars[j];
            chars[j] = t;
            ++i;
            --j;
        }
        return new String(chars);
    }
}

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