409. 最长回文串

https://leetcode-cn.com/problems/longest-palindrome/

func longestPalindrome(_ s: String) -> Int {
    //存储每个字符出现的次数
    var dic = Dictionary<Character,Int>()
    for char in s {
        if dic.keys.contains(char) {
            var charCount = dic[char]!
            charCount = charCount + 1
            dic.updateValue(charCount, forKey: char);
        } else {
            dic.updateValue(1, forKey: char);
        }
    }
    //遍历key，count为偶数说明可以组成左右对称，奇数最后余1当做中心
    var result = 0
    for (_, cout) in dic {
        if cout & 1 == 0 {//偶数
            result = result + cout
        }
        if cout & 1 == 1 {//奇数
            result = result + (cout - 1)
        }
    }
    result = result < s.count ? result + 1 : result
    return result
}