Zomato Software Development Engineer SDE interview questions

Dsa questions based on trees

this was the DSA question I got. An array is called neat if it can be obtained by the concatenation of an arbitrary number of blocks (possibly zero). Note that an empty array is always neat. You are given an array a consisting of n integers. Find the length of its longest neat subsequence. A sequence c is a subsequence of a sequence a if c can be obtained from a by the deletion of several (possibly zero or all) elements from arbitrary positions.