# Longest Uncommon Subsequence I Problem

## Description

LeetCode Problem 521.

Given two strings a and b, return the length of the longest uncommon subsequence between a and b. If the longest uncommon subsequence does not exist, return -1.

An uncommon subsequence between two strings is a string that is a subsequence of one but not the other.

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:

``````1
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Input: a = "aba", b = "cdc"
Output: 3
Explanation: One longest uncommon subsequence is "aba" because "aba" is a subsequence of "aba" but not "cdc".
Note that "cdc" is also a longest uncommon subsequence.
``````

Example 2:

``````1
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Input: a = "aaa", b = "bbb"
Output: 3
Explanation:The longest uncommon subsequences are "aaa" and "bbb".
``````

Example 3:

``````1
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Input: a = "aaa", b = "aaa"
Output: -1
Explanation:Every subsequence of string a is also a subsequence of string b. Similarly, every subsequence of string b is also a subsequence of string a.
``````

Constraints:

• 1 <= a.length, b.length <= 100
• a and b consist of lower-case English letters.

## Sample C++ Code

``````1
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class Solution {
public:
int findLUSlength(string a, string b) {
if (a == b)
// There is no subsequence in a that is not in b. return -1.
return -1;
else
// If a.size() == b.size() but a != b, return the length of a and b.
// If a.size() != b.size(), we can return the maximum length.
return max(a.size(), b.size());
}
};
``````