// Runtime: 1 ms, faster than 97.30% of Java online submissions for Permutations.
// Memory Usage: 37.4 MB, less than 95.74% of Java online submissions for Permutations.

class Solution {
    public List<List<Integer>> permute(int[] nums) {
        ArrayList<List<Integer>> result = new ArrayList<>();
        permute(nums, nums.length, new ArrayList<>(), result, new boolean[nums.length]);
        return result;
    }

    void permute(int[] nums, int n, List<Integer> current, List<List<Integer>> result, boolean[] chosen) {
        if (current.size() == n) {
            result.add(new ArrayList<>(current));
            return;
        }

        for (int i = 0; i < n; i++) {
            if (chosen[i]) {
                continue;
            }
            chosen[i] = true;
            current.add(nums[i]);
            permute(nums, n, current, result, chosen);
            current.remove(current.size() - 1);
            chosen[i] = false;
        }
    }
}