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()
{
cout << longestPalindrome("civilwartestingwhetherthatnaptionoranynartionsoconceivedandsodedicatedcanlongendureWeareqmetonagreatbattlefiemldoftzhatwarWehavecometodedicpateaportionofthatfieldasafinalrestingplaceforthosewhoheregavetheirlivesthatthatnationmightliveItisaltogetherfangandproperthatweshoulddothisButinalargersensewecannotdedicatewecannotconsecratewecannothallowthisgroundThebravelmenlivinganddeadwhostruggledherehaveconsecrateditfaraboveourpoorponwertoaddordetractTgheworldadswfilllittlenotlenorlongrememberwhatwesayherebutitcanneverforgetwhattheydidhereItisforusthelivingrathertobededicatedheretotheulnfinishedworkwhichtheywhofoughtherehavethusfarsonoblyadvancedItisratherforustobeherededicatedtothegreattdafskremainingbeforeusthatfromthesehonoreddeadwetakeincreaseddevotiontothatcauseforwhichtheygavethelastpfullmeasureofdevotionthatweherehighlyresolvethatthesedeadshallnothavediedinvainthatthisnationunsderGodshallhaveanewbirthoffreedomandthatgovernmentofthepeoplebythepeopleforthepeopleshallnotperishfromtheearth") << endl;
cout << endl;
cout << longestPalindrome("dccaccddccaccddccaccddccaccd") << endl;
cout << endl;
}
Last modified 4yr ago