【leetcode】1704. Determine if String Halves Are Alike

题目如下：

You are given a string s of even length. Split this string into two halves of equal lengths, and let a be the first half and b be the second half.

Two strings are alike if they have the same number of vowels ('a', 'e', 'i', 'o', 'u', 'A', 'E', 'I', 'O', 'U'). Notice that s contains uppercase and lowercase letters.

Return true if a and b are alike. Otherwise, return false.

Example 1:

Input: s = "book"
Output: true
Explanation: a = "bo" and b = "ok". a has 1 vowel and b has 1 vowel. Therefore, they are alike.

Example 2:

Input: s = "textbook"
Output: false
Explanation: a = "text" and b = "book". a has 1 vowel whereas b has 2. Therefore, they are not alike.
Notice that the vowel o is counted twice.

Constraints:

• 2 <= s.length <= 1000
• s.length is even.
• s consists of uppercase and lowercase letters.

解题思路：很简单的题目，可以采用头尾指针的方法，左边遇到元音加一，右边遇到元音减一，最后判断结果是否为零即可。

代码如下：

class Solution(object):
    def halvesAreAlike(self, s):
        """
        :type s: str
        :rtype: bool
        """
        count = 0
        voewls = ('a', 'e', 'i', 'o', 'u', 'A', 'E', 'I', 'O', 'U')
        for i in range(len(s)/2):
            if s[i] in voewls:
                count +=1
            if s[len(s)/2+i] in voewls:
                count -= 1
        return count == 0