409. Longest Palindrome

FreeeLinux

于 2017-03-13 02:27:16 发布

阅读量389

点赞数

CC 4.0 BY-SA版权

分类专栏： Leetcode

本文链接：https://blog.youkuaiyun.com/FreeeLinux/article/details/61828242

Leetcode 专栏收录该内容

64 篇文章

订阅专栏

本文介绍了一种高效的算法，用于从给定字符串中构建最长的回文子串。通过使用C++实现，并针对LeetCode题目进行解答，该算法考虑了大小写敏感性并确保了在1,010长度内的字符串能够快速求解。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

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.

下面是我的6ms C++ Solution，还在leetcode上分享了：

class Solution {
public:
    int longestPalindrome(string s) {
        if(s.length() == 0)
            return 0;
        int ans = 0;
        unordered_map<char, int> umap;
        for(auto c : s)
            umap[c]++;
        for(auto c : s){
            ans += umap[c] / 2;
            umap[c] = 0;
        }
        ans = ans * 2 + 1;
        return ans > s.length() ? s.length() : ans;
    }
};