1
var subsets = function (nums) {
2
  const res = [];
3

4
  const dfs = (i, slate) => {
5
    if (i == nums.length) {
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      res.push(slate.slice());
7

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      return;
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    }
10

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    // take the current number into the subset.
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    slate.push(nums[i]);
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    dfs(i + 1, slate);
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    slate.pop();
15

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    // ignore the current number.
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    dfs(i + 1, slate);
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  };
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  dfs(0, []);
21

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  return res;
23
};