[LeetCode] Problem 90 - Subsets II

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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:

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[
  [2],
  [1],
  [1,2,2],
  [2,2],
  [1,2],
  []
]

Code

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public List<List<Integer>> subsetsWithDup(int[] nums) {
    List<List<Integer>> result = new ArrayList<>();

    Arrays.sort(nums);
    subsetsWithDupHelper(result, new ArrayList<>(), nums, 0);
    return result;
}

private void subsetsWithDupHelper(List<List<Integer>> result, List<Integer> subset, int[] nums, int idx) {
    result.add(new ArrayList<>(subset));

    for (int i = idx; i < nums.length; i++) {
        if (i > idx && nums[i] == nums[i - 1])
            continue;

        subset.add(nums[i]);
        subsetsWithDupHelper(result, subset, nums, i + 1);
        subset.remove(subset.size() - 1);
    }
}