2900. Longest Unequal Adjacent Groups Subsequence I

Problem Statement

You are given an integer n, a 0-indexed string array words, and a 0-indexed binary array groups, both arrays having length n.

You need to select the longest subsequence from an array of indices [0, 1, ..., n - 1], such that for the subsequence denoted as [i0, i1, ..., ik - 1] having length k, groups[ij] != groups[ij + 1], for each j where 0 < j + 1 < k.

Return a string array containing the words corresponding to the indices (in order) in the selected subsequence. If there are multiple answers, return any of them.

A subsequence of an array is a new array that is formed from the original array by deleting some (possibly none) of the elements without disturbing the relative positions of the remaining elements.

Note: strings in words may be unequal in length.

Example 1:

Input: n = 3, words = ["e","a","b"], groups = [0,0,1]
Output: ["e","b"]
Explanation: A subsequence that can be selected is [0,2] because groups[0] != groups[2].
So, a valid answer is [words[0],words[2]] = ["e","b"].
Another subsequence that can be selected is [1,2] because groups[1] != groups[2].
This results in [words[1],words[2]] = ["a","b"].
It is also a valid answer.
It can be shown that the length of the longest subsequence of indices that satisfies the condition is 2.

Example 2:

Input: n = 4, words = ["a","b","c","d"], groups = [1,0,1,1]
Output: ["a","b","c"]
Explanation: A subsequence that can be selected is [0,1,2] because groups[0] != groups[1] and groups[1] != groups[2].
So, a valid answer is [words[0],words[1],words[2]] = ["a","b","c"].
Another subsequence that can be selected is [0,1,3] because groups[0] != groups[1] and groups[1] != groups[3].
This results in [words[0],words[1],words[3]] = ["a","b","d"].
It is also a valid answer.
It can be shown that the length of the longest subsequence of indices that satisfies the condition is 3.

Constraints:

1 <= n == words.length == groups.length <= 100
1 <= words[i].length <= 10
0 <= groups[i] < 2
words consists of distinct strings.
words[i] consists of lowercase English letters.

Intuition

Approach:

Think of This as LIS, 
Why LIS
We want longest sequence where adjacents are not same

So when ajacent groupid a

Video Links

Approach 1:

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Approach 2:

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Approach 3:

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Approach 4:

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