Reverse_Vowels_of_a_String.md

345. Reverse Vowels of a String

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

Example 1:

Given s = "hello", return "holle".

Example 2:

Given s = "leetcode", return "leotcede".

Note: The vowels does not include the letter "y".

Method:

two pointers:

to check contains for O(1), we can use dict or set:

class Solution(object):
    def reverseVowels(self, s):
        """
        :type s: str
        :rtype: str
        """
        l=list(s)
        d={'a':1, 'e':1, 'i':1, 'o':1, 'u':1}
        i, j=0, len(l)-1
        while i<j:
            while l[i].lower() not in d and i<j:
                i+=1
            while l[j].lower() not in d and i<j:
                j-=1
            if i<j:
                l[i], l[j]=l[j], l[i]
                i+=1
                j-=1
        return ''.join(l)