/**
     * 535 异或大法。这应该是这个题最正常的解法了。当然可以直接将传参返回给题目~~
     * 也可以用map去存储每一个shortUrl和longUrl之间的映射
     */
    private static final int FACTOR = 20000;

    public String encode(String longUrl) {
        char[] chars = longUrl.toCharArray();
        for (int i = 0; i < chars.length; i++) {
            chars[i] = (char) (chars[i] ^ FACTOR);
        }
        return String.valueOf(chars);
    }

    public String decode(String shortUrl) {
        return encode(shortUrl);
    }