409. Longest Palindrome（python+cpp）

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题目：

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.

解释：
主要考虑字母在字符串中出现的次数是奇数次还是偶数次。
python代码：

from collections import Counter
class Solution(object):
    def longestPalindrome(self, s):
        """
        :type s: str
        :rtype: int
        """
        result=0
        have_odd=False
        _dict=Counter(s)
        for key in _dict:
            if _dict[key]%2==0:
                result+=_dict[key]
            else:
                result+=_dict[key]-1
                have_odd=True
        return result+1 if have_odd else result   

c++代码：

class Solution {
public:
    int longestPalindrome(string s) {
        map<char,int> count_map;
        for(auto letter:s)
            count_map[letter]+=1;
        int result=0;
        bool have_odd=false;
        for(auto &item:count_map)
        {
            if(item.second%2==0)
                result+=item.second;
            else
            {
                result+=item.second-1;
                have_odd=true;
            }
        }
        return have_odd?result+1:result;
    }
};

总结：
相比之下，字典真的是太省时间了。