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.
Assume the length of given string will not exceed 1,010.
Input: “abccccdd” Output: 7 Explanation: One longest palindrome that can be built is “dccaccd”, whose length is 7.
Thanks to a brilliant idea from one coder. Use the logic true/false cases to achieve fast run time. Add length by two each time when evaluate. No adding when flipped odd times. In this way, only the even numbered appearance is calculated.