0345-reverse-vowels-of-a-string

345. Reverse Vowels of a String

Problem Description

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

Detail instruction can be found here.

Example 1:

Input: "hello"
Output: "holle"

Example 2:

Input: "leetcode"
Output: "leotcede"

Solution

Approach: Two Pointers

public String reverseVowels(String s) {
    char[] chars = s.toCharArray();
    int lo = 0, hi = s.length() - 1;
    
    while (lo < hi) {
        if (isVowel(chars[lo]) && isVowel(chars[hi])) {
            char t = chars[lo];
            chars[lo] = chars[hi];
            chars[hi] = t;
            lo++; hi--;
        }
        if (!isVowel(chars[lo]))
            lo++;
        if (!isVowel(chars[hi]))
            hi--;
    }
    return new String(chars);
}

private helper methods

public boolean isVowel(char c) {
    return "AEIOUaeiou".indexOf(c) != -1;
}

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