The Maximum Size of a Set After Removals coding problem gives you two arrays, nums1 and nums2, both of size n. You must remove n/2 elements from each array. After these removals, you combine the remaining elements of both arrays into a single set. The goal is to maximize the number of unique elements in this final set.
This "Medium" problem is used by Microsoft and Amazon to test a candidate's logical reasoning and greedy thinking. It's not about complex data structures; it's about correctly categorizing elements (those unique to nums1, those unique to nums2, and those in both) and deciding which to keep to maximize the unique count.
This follows the Hash Table and Greedy interview pattern. Use sets to find unique elements in nums1, unique elements in nums2, and their intersection. Let c1 be unique to nums1, c2 be unique to nums2, and common be elements in both. We can take up to n/2 elements from the nums1 side and n/2 from the nums2 side. We greedily pick unique ones first, then use the common ones to fill any remaining "slots" up to the n/2 limit.
n=4. nums1: [1, 2, 1, 2], nums2: [3, 4, 3, 4].
Candidates often over-complicate the logic by trying to simulate the removals. The key is to realize you are actually picking n/2 elements to keep. Another error is not properly accounting for the "common" elements, which can be picked from either side but only count once in the final set.
In "Array, Hash Table, Greedy interview pattern" questions, Venn diagrams are your best friend. Visualize the sets of elements and their overlaps to clearly see how many "unique" and "common" elements are available to contribute to your final result.
