> For the complete documentation index, see [llms.txt](https://dfine.gitbook.io/leetcode/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://dfine.gitbook.io/leetcode/521.longest_uncommon_subsequence_i.md).

# 521.Longest Uncommon Subsequence I

**521.Longest Uncommon Subsequence I**

难度:Easy

> 给定两个字符串，你需要从这两个字符串中找出最长的特殊序列。最长特殊序列定义如下：该序列为某字符串独有的最长子序列（即不能是其他字符串的子序列）。

子序列可以通过删去字符串中的某些字符实现，但不能改变剩余字符的相对顺序。空序列为所有字符串的子序列，任何字符串为其自身的子序列。

输入为两个字符串，输出最长特殊序列的长度。如果不存在，则返回 -1。

```
示例 :

输入: "aba", "cdc"
输出: 3
解析: 最长特殊序列可为 "aba" (或 "cdc")
说明:
两个字符串长度均小于100。
字符串中的字符仅含有 'a'~'z'。
```

脑筋急转弯？没看出这题的意义。。。代码如下：

```
class Solution {
public:
    int findLUSlength(string a, string b) {
        int flag=1;
        if(b.length()<a.length()) swap(a,b);
        if(b.length()==0)
            return -1;
        if(a.length()==b.length())
            if(a==b) flag=0;

        return flag? b.length(): -1;
        
    }
};
```


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://dfine.gitbook.io/leetcode/521.longest_uncommon_subsequence_i.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.