問題

給定兩個字串，你需要從這兩個字串中找出最長的特殊序列。最長特殊序列定義如下：該序列為某字串獨有的最長子序列（即不能是其他字串的子序列）。

子序列可以通過刪去字串中的某些字元實現，但不能改變剩餘字元的相對順序。空序列為所有字串的子序列，任何字串為其自身的子序列。

輸入為兩個字串，輸出最長特殊序列的長度。如果不存在，則返回 -1。

輸入: "aba", "cdc"

輸出: 3

解析: 最長特殊序列可為 "aba" (或 "cdc")

說明:

兩個字串長度均小於100。
字串中的字元僅含有 'a'~'z'。

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.

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:

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

示例

public class Program {

    public static void Main(string[] args) {
        var a = "Iori's Blog";
        var b = "aba";

        var res = FindLUSlength(a, b);
        Console.WriteLine(res);

        Console.ReadKey();
    }

    private static int FindLUSlength(string a, string b) {
        //真不知道這道題存在的意思是什麼
        if(a == b) return -1;
        return Math.Max(a.Length, b.Length);
    }

}

以上給出1種演算法實現，以下是這個案例的輸出結果：

11

分析：

顯而易見，以上演算法的時間複雜度為  。