Determine if String Halves Are Alike — LeetCode 1704 Python Solution

The problem

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.

Example

Input

s = "book"

Output

true

Explanation

a = "bo" and b = "ok". a has 1 vowel and b has 1 vowel. Therefore, they are alike.

Python solution

class Solution:
    def halvesAreAlike(self, s: str) -> bool:
        cnt, n = 0, len(s) >> 1
        vowels = set('aeiouAEIOU')
        for i in range(n):
            cnt += s[i] in vowels
            cnt -= s[i + n] in vowels
        return cnt == 0

Complexity

Pattern: Hash Map

Trade memory for time: remember what you have seen so the second pass never happens. LeetCode 1704. Determine if String Halves Are Alike is filed here on both counts: the reference solution below belongs to the algorithm family this hub collects, and LeetCode tags it Counting.

The hash map guide has the Python template for the pattern and the 709 LeetCode problems that use it.

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