Day12 - 409. Longest Palindrome

今日题目：409. Longest Palindrome

Given a string s which consists of lowercase or uppercase letters, return the length of the longest palindrome that can be built with those letters.
Letters are case sensitive, for example, "Aa" is not considered a palindrome here.

Example 1:
Input: s = "abccccdd"
Output: 7
Explanation:
One longest palindrome that can be built is "dccaccd", whose length is 7.

Example 2:
Input: s = "a"
Output: 1

解题技巧

1. str.count(sub, start= 0,end=len(string))

str = 'banana pie banana'
str.count('a',2)
->5

2. collections.Counter()

str2 = 'gallahad'

• c = Counter(str2)
  ->Counter({'a': 3, 'n': 2, 'b': 1, 's': 1})

• Counter.items()->['a': 3, 'n': 2, 'b': 1, 's': 1]

• Counter.values()->[3,2,1,1]

• Counter.keys()->['a','n','b','s']

My solution

class Solution:
    def longestPalindrome(self, s: str) -> int:
        n = len(s)
        c = collections.Counter(s)
    
        ans = 0
        odd = 0
        
        for v in c.values():
            ans += int(v/2)*2

            if ans%2 ==0 and v%2==1:
                ans +=1
        return ans

Result