README_EN.md

345. Reverse Vowels of a String

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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 lower and upper cases, more than once.

 

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);
    }
}

Go

func reverseVowels(s string) string {
	left, right := 0, len(s)-1
	a := []byte(s)
	for left < right {
		for left < right && !isVowel(a[left]) {
			left++
		}
		for left < right && !isVowel(a[right]) {
			right--
		}
		if left != right && isVowel(a[left]) && isVowel(a[right]) {
			a[left], a[right] = a[right], a[left]
			left++
			right--
		}
	}
	return string(a)
}

func isVowel(b byte) bool {
	return b == 'a' || b == 'e' || b == 'i' || b == 'o' || b == 'u' ||
		b == 'A' || b == 'E' || b == 'I' || b == 'O' || b == 'U'
}

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