409. Longest Palindrome

Given a string which consists of lowercase or uppercase letters, find the length of the longest palindromes that can be built with those letters.

This is case sensitive, for example"Aa"is not considered a palindrome here.

Note: Assume the length of given string will not exceed 1,010.

Example:

Input:"abccccdd"

Output:7

Explanation:
One longest palindrome that can be built is "dccaccd", whose length is 7.

Thoughts:

1. Total len - number of odds + 1 (indicator of whether odds > 0)

Code: Python

class Solution(object):
    def longestPalindrome(self, s):
        odds = sum(v & 1 for v in collections.Counter(s).values())
        return len(s) - odds + bool(odds)

Code: Python with counting even number (slower)

class Solution(object):
    def longestPalindrome(self, s):
        even = sum(v & ~1 for v in collections.Counter(s).values())
        return even + (even < len(s))