90. Subsets II (Medium)

https://leetcode.com/problems/subsets-ii/

Given a collection of integers that might contain duplicates, nums, return all possible subsets (the power set).

Note: The solution set must not contain duplicate subsets.

Example:

Input: [1,2,2]
Output:
[
  [2],
  [1],
  [1,2,2],
  [2,2],
  [1,2],
  []
]

Solutions

class Solution {
    Set<String> strSet = new HashSet<>();

    public List<List<Integer>> subsetsWithDup(int[] nums) {
        Arrays.sort(nums);

        List<List<Integer>> ans = new ArrayList<>();

        List<Integer> track = new ArrayList<>();

        combine(0, nums, track, ans);

        return ans;
    }

    private void combine(int depth, int[] nums, List<Integer> track, List<List<Integer>> ans) {
        if (depth == nums.length) {
            if (!strSet.add(track.toString())) {
                return;
            }

            List<Integer> sol = new ArrayList<>(track);

            ans.add(sol);

            return;
        }

        track.add(nums[depth]);
        combine(depth + 1, nums, track, ans);
        track.remove(track.size()-1);

        combine(depth + 1, nums, track, ans);
    }
}

Incorrect Solutions

References

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