345. Reverse Vowels of a String

Problem

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 * 10^5

• s consist of printable ASCII characters.

Solution

class Solution {
    private boolean isVowel(char c) {
        return c == 'a' || c == 'A' || c == 'e' || c == 'E' || c == 'i' || c == 'I' || c == 'o'
                || c == 'O' || c == 'u' || c == 'U';
    }

    public String reverseVowels(String str) {
        int i = 0;
        int j = str.length() - 1;
        char[] str1 = str.toCharArray();
        while (i < j) {
            if (!isVowel(str1[i])) {
                i++;
            } else if (!isVowel(str1[j])) {
                j--;
            } else {
                // swapping
                char t = str1[i];
                str1[i] = str1[j];
                str1[j] = t;
                i++;
                j--;
            }
        }
        return String.copyValueOf(str1);
    }
}

Explain:

nope.

Complexity:

• Time complexity : O(n).
• Space complexity : O(n).