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# LeetCode 345. Reverse Vowels of a String (javascript solution)

### 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.

### Solution:

Time Complexity : O(n)
Space Complexity: O(1)

``````// Two pointers
var reverseVowels = function(s) {
// Helper function to check if the current letter is a vowel
function isVowel(letter) {
const vowels = {
a: 'a', e:'e', i:'i', o: 'o', u:'u'
}
return vowels[letter.toLowerCase()]
}

// Left and right pointers
let left = 0, right = s.length-1
// Split s into an array so we can swap letters (string are immuatable)
s = s.split('')
while(left < right) {
// Check if pointers are pointing to a vowel
const l = isVowel(s[left]), r = isVowel(s[right])
// If both are vowels swap
if(l && r) {
const temp = s[left]
s[left] = s[right]
s[right] = temp
left++
right--
} else if(!l && !r) { // If both are not vowels move both pointers
left++
right--
} else if(!l) { // Move left pointer
left++
} else { // Mover right pointer
right--
}
}
// Join array to a string
return s.join('');
};
``````