409. Longest Palindrome

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題目敘述

Given a string s which consists of lowercase or uppercase letters, return the length of the longest palindrome that can be built with those letters.

Letters are case sensitive, for example, "Aa" is not considered a palindrome.

Palindrome A palindrome is a string that reads the same forward and backward.

Example 1

Input: s = “abccccdd” Output: 7 Explanation: One longest palindrome that can be built is “dccaccd”, whose length is 7.

Example 2

Input: s = “a” Output: 1 Explanation: The longest palindrome that can be built is “a”, whose length is 1.

解題思路

Solution

class Solution {
    public int longestPalindrome(String s) {
        int[] hashtable = new int[52];
        for (char c : s.toCharArray()) {
            if (c >= 'a' && c <= 'z')  hashtable[c - 'a']++;
            else hashtable[c - 'A' + 26]++;
        }

        int result = 0;
        boolean hasOdd = false;
        for (int value : hashtable) {
            if(value % 2 == 0) {
                result += value;
            } else {
                result += value - 1;
                hasOdd = true;
            }
        }

        return hasOdd ? result + 1 : result;
    }
}