# 0522. Longest Uncommon Subsequence II

<https://leetcode.com/problems/longest-uncommon-subsequence-ii>

## Description

Given an array of strings `strs`, return *the length of the **longest uncommon subsequence** between them*. If the longest uncommon subsequence does not exist, return `-1`.

An **uncommon subsequence** between an array of strings is a string that is a **subsequence of one string but not the others**.

A **subsequence** of a string `s` is a string that can be obtained after deleting any number of characters from `s`.

* For example, `"abc"` is a subsequence of `"aebdc"` because you can delete the underlined characters in `"aebdc"` to get `"abc"`. Other subsequences of `"aebdc"` include `"aebdc"`, `"aeb"`, and `""` (empty string).

**Example 1:**

```
**Input:** strs = ["aba","cdc","eae"]
**Output:** 3
```

**Example 2:**

```
**Input:** strs = ["aaa","aaa","aa"]
**Output:** -1
```

**Constraints:**

* `2 <= strs.length <= 50`
* `1 <= strs[i].length <= 10`
* `strs[i]` consists of lowercase English letters.

## ac

```java
class Solution {
    public int findLUSlength(String[] strs) {
        // edge cases

        // sort the array in length desc
        // Arrays.sort(strs, (a, b) -> {return b.length() - a.length();});

        // check 
        int max = -1;
        for (int i = 0; i < strs.length; i++) {
            boolean valid = true;
            for (int j = 0; j < strs.length && valid; j++) {
                if (i == j) continue;
                if (isSubsequence(strs[i], strs[j])) valid = false;
            }
            if (valid) max = Math.max(max, strs[i].length());
        }

        return max;
    }

    private boolean isSubsequence(String s1, String s2) {
        int i1 = 0, i2 = 0;
        while (i1 < s1.length() && i2 < s2.length()) {
            if (s1.charAt(i1) == s2.charAt(i2)) {
                i1++;
            }
            i2++;
        }
        return i1 == s1.length();
    }
}
/*
for each string, check if it is subsequence of previous string, if yes continue to check next one.
*/
```