# 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.
Notes:
• Unsure why this doesnt work. The largest palindromic substring length are all the even characters + the largest character that goes directly in the center.
int longestPalindrome(string s)
{
//cout << s.length() << endl;
unordered_map<char, int> char_freq;
char_freq.reserve(26 * 2); // letters + capital
for (char c : s) {
if (char_freq.find(c) != char_freq.end())
char_freq[c]++;
else char_freq.insert(make_pair(c, 1));
}
int max_odd_i = 0;
int length = 0;
for (auto i : char_freq) {
if (i.second % 2 != 0 && i.second > max_odd_i)
max_odd_i = i.second;
else if (i.second % 2 == 0)
length += i.second;
}
return length + max_odd_i;
}
int main()
{