Leetcode409. Longest Palindrome

Posted 2022-12-08 wuezs

题目链接：https://leetcode.com/contest/7/problems/longest-palindrome/

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.

思路：
easy 统计每种字符出现次数，分奇偶情况讨论。

算法：

    public int longestPalindrome(String s) 
        if (s.length() == 0)
            return 0;
        int lm[] = new int[26];
        int um[] = new int[26];

        for (char c : s.toCharArray()) 
            if (Character.isLowerCase(c))
                lm[c - 'a']++;
            else
                um[c - 'A']++;
        

        int count = 0;
        boolean flag = false;// 是否有单个字符

        for (int num : lm) 
            if (num % 2 == 0) 
                count += num;
             else 
                if (flag) 
                    count += num - 1;
                 else 
                    count += num;
                    flag = true;
                
            
        

        for (int num : um) 
            if (num % 2 == 0) 
                count += num;
             else 
                if (flag) 
                    count += num - 1;
                 else 
                    count += num;
                    flag = true;
                
            
        

        return count;