522. 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.
Solutions
Solution 1: Subsequence Judgment
We define a function $check(s, t)$ to determine whether string $s$ is a subsequence of string $t$. We can use a two-pointer approach, initializing two pointers $i$ and $j$ to point to the beginning of strings $s$ and $t$ respectively, then continuously move pointer $j$. If $s[i]$ equals $t[j]$, then move pointer $i$. Finally, check if $i$ equals the length of $s$. If $i$ equals the length of $s$, it means $s$ is a subsequence of $t$.
To determine if string $s$ is unique, we only need to take string $s$ itself and compare it with other strings in the list. If there exists a string for which $s$ is a subsequence, then $s$ is not unique. Otherwise, string $s$ is unique. We take the longest string among all unique strings.
The time complexity is $O(n^2 \times m)$, where $n$ is the length of the list of strings, and $m$ is the average length of the strings. The space complexity is $O(1)$.
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