24. leetcode 409. Longest Palindrome

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.

思路：求所给字符串中的字符所能构成的最长回文串（正读反读都一样）的长度。取决于出现次数为奇数次的字符。