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class Solution {
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  public List<List<Integer>> permuteUnique(int[] nums) {
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    List<List<Integer>> ans = new ArrayList<>();
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    Arrays.sort(nums);
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    boolean used[] = new boolean[nums.length];
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    permutationsFinder(nums, ans, new ArrayList<>(), used);
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    return ans;
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  }
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  static void permutationsFinder(
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      int[] nums, List<List<Integer>> ans, List<Integer> list, boolean used[]) {
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    if (list.size() == nums.length) {
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      ans.add(new ArrayList<>(list));
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      return;
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    }
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    for (int i = 0; i < nums.length; i++) {
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      if (used[i]) continue;
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      if (i > 0 && nums[i] == nums[i - 1] && !used[i - 1]) continue;
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      list.add(nums[i]);
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      used[i] = true;
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      permutationsFinder(nums, ans, list, used);
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      list.remove(list.size() - 1);
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      used[i] = false;
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    }
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  }
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}