[LeetCode][Python]521. Longest U

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.

思路：

1. 一开始的时候我还想着怎么去找不同的字符。后来看了其他人的解答，才意识到当两个字符串不等的时候，较长的那个不可能是较短的那个的子串。

return -1 if a==b else max(len(a), len(b))
return a!=b and max(len(a),len(b))or-1
return(a!=b)*max(len(a),len(b))or-1