A recursive approach (which is what I would use) would involve breaking the problem into isomorphic subproblems: to find all permutations of a string, find all permutations of the string without a ...

You are given a string s, which may contain duplicate characters. Your task is to generate and return an array of all unique permutations of the string. You can return the permutations in any order.

You are given a string s, which may contain duplicate characters. Your task is to generate and return an array of all unique permutations of the string. You can return the permutations in any order.