leetcode 409. Longest Palindrome

/*leetcode 409. Longest PalindromeGiven 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:7Explanation:One longest palindrome that can be built is "dccaccd", whose length is 7.题目大意：对于给定的字符串，用这些字符能组成的最长回文是多长。解题思路：最长回文长度计算方法：如果出现偶数次，则直接加上；如果出现奇数次，第一个基数加上奇数次，后面的基数只能取奇数次-1.*/#include <iostream>#include <vector>#include <string>#include <algorithm>using namespace std;class Solution {public:    int longestPalindrome(string s) {        int len = s.size();        if (len == 0 || len == 1)            return len;        vector<int> v(128, 0);        for (int i = 0; i < len; ++i)            ++v[s[i]];        int ret = 0;        int oddNum = 0;        for (int i = 0; i < 128; ++i)        {            if (v[i] & 0x01)            {                ++oddNum;            }            ret += v[i];        }        if (oddNum)            ret -= (--oddNum);        return ret;    }};void test(){    Solution sol;    cout << sol.longestPalindrome("civilwartestingwhetherthatnaptionoranynartionsoconceivedandsodedicatedcanlongendureWeareqmetonagreatbattlefiemldoftzhatwarWehavecometodedicpateaportionofthatfieldasafinalrestingplaceforthosewhoheregavetheirlivesthatthatnationmightliveItisaltogetherfangandproperthatweshoulddothisButinalargersensewecannotdedicatewecannotconsecratewecannothallowthisgroundThebravelmenlivinganddeadwhostruggledherehaveconsecrateditfaraboveourpoorponwertoaddordetractTgheworldadswfilllittlenotlenorlongrememberwhatwesayherebutitcanneverforgetwhattheydidhereItisforusthelivingrathertobededicatedheretotheulnfinishedworkwhichtheywhofoughtherehavethusfarsonoblyadvancedItisratherforustobeherededicatedtothegreattdafskremainingbeforeusthatfromthesehonoreddeadwetakeincreaseddevotiontothatcauseforwhichtheygavethelastpfullmeasureofdevotionthatweherehighlyresolvethatthesedeadshallnothavediedinvainthatthisnationunsderGodshallhaveanewbirthoffreedomandthatgovernmentofthepeoplebythepeopleforthepeopleshallnotperishfromtheearth") << endl;}int main(){    test();    return 0;}