266. Palindrome-Permutation.md

Description

Given a string, determine if a permutation of the string could form a palindrome.

Example 1:

Input: "code"
Output: false

Example 2:

Input: "aab"
Output: true

Example 3:

Input: "carerac"
Output: true

---

python solution

• 如果len(s) % 2 = 0, 那么每个元素必须成对出现。如果len(s) % 2 = 1, 那么除了一个元素数量为奇数外，其他的必须为偶数。

from collections import Counter


class Solution:
    def canPermutePalindrome(self, s):
        """
        :type s: str
        :rtype: bool
        """
        c = Counter(s)
        if len(s) % 2 == 0:
            return sum(map(lambda c: c % 2 == 1, c.values())) == 0
        return sum(map(lambda c: c % 2 == 1, c.values())) == 1