2900 - Longest Unequal Adjacent Groups Subsequence I.

Medium

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 <code>i₀, i₁, ..., i_{k - 1}</code> having length k, <code>groupsi_j != groupsi_{j + 1}</code>, 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 groups0 != groups2.

So, a valid answer is [words0,words2] = "e","b".

Another subsequence that can be selected is 1,2 because groups1 != groups2.

This results in [words1,words2] = "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 groups0 != groups1 and groups1 != groups2.

So, a valid answer is [words0,words1,words2] = "a","b","c".

Another subsequence that can be selected is 0,1,3 because groups0 != groups1 and groups1 != groups3.

This results in [words0,words1,words3] = "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.