Generate unique permutations with duplicates
Company: Meta
Role: Machine Learning Engineer
Category: Coding & Algorithms
Difficulty: medium
Interview Round: Onsite
Given an array of integers that may contain duplicates, generate all unique permutations. Ensure no duplicate permutations are returned even if some values occur more than twice. Describe your algorithm (e.g., backtracking with frequency counts), prove correctness, and analyze time and space complexity.
Overview: This question evaluates a candidate's understanding of permutation generation and duplicate handling within algorithm design, testing combinatorial reasoning, correctness proofs, and time/space complexity analysis.