1
var permuteUnique = function (nums) {
2
  const answer = [];
3

4
  function perm(pos, array) {
5
    if (pos >= array.length) {
6
      answer.push(array);
7
    }
8

9
    const setObject = new Set();
10

11
    for (let index = pos; index < array.length; index++) {
12
      if (setObject.has(array[index])) {
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        continue;
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      }
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      setObject.add(array[index]);
16

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      // swap numbers
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      let temp = array[pos];
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      array[pos] = array[index];
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      array[index] = temp;
21

22
      perm(pos + 1, [...array]);
23

24
      // undo swapping for next iteration
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      temp = array[index];
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      array[index] = array[pos];
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      array[pos] = temp;
28
    }
29
  }
30

31
  perm(0, nums);
32

33
  return answer;
34
};