Given a group of two strings, you need to find the longest uncommon subsequence of this group of two strings. The longest uncommon subsequence is defined as the longest subsequence of one of these strings and this subsequence should not be any subsequence of the other strings.

A subsequence is a sequence that can be derived from one sequence by deleting some characters without changing the order of the remaining elements. Trivially, any string is a subsequence of itself and an empty string is a subsequence of any string.

The input will be two strings, and the output needs to be the length of the longest uncommon subsequence. If the longest uncommon subsequence doesn't exist, return -1.

Example 1:

Input: "aba", "cdc"
Output: 3
Explanation: The longest uncommon subsequence is "aba" (or "cdc"), 
because "aba" is a subsequence of "aba", 
but not a subsequence of any other strings in the group of two strings. 

Note:

1. Both strings' lengths will not exceed 100.
2. Only letters from a ~ z will appear in input strings.

這道題是在4月1號出的，有人說這是愚人節最好的禮物，哈哈～這道題只是為了後面那道題做鋪墊，不過這題確實簡單啊，兩個字串的情況很少，如果兩個字串相等，那麼一定沒有非共同子序列，反之，如果兩個字串不等，那麼較長的那個字串就是最長非共同子序列，參見程式碼如下：

class Solution {
public:
    int findLUSlength(string
 
 a, string b) {
        return a == b ? -1 : max(a.size(), b.size());
    }
};