Given a collection of distinct integers, return all possible permutations.

1
2
3
4
5
6
7
8
9
10
Input: [1,2,3]
Output:
[
  [1,2,3],
  [1,3,2],
  [2,1,3],
  [2,3,1],
  [3,1,2],
  [3,2,1]
]
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
class Solution {
    public List<List<Integer>> permute(int[] nums) {
        List<List<Integer>> list = new ArrayList<>();
        dfs(list, new ArrayList<>(), nums);
        return list;
    }
    
    public void dfs(List<List<Integer>> list, List<Integer> arr, int[] nums) {
        if (arr.size() == nums.length) list.add(new ArrayList<>(arr));
        for (int i = 0; i < nums.length; ++i) {
            if (arr.contains(nums[i])) continue;
            arr.add(nums[i]);
            dfs(list, arr, nums);
            arr.remove(arr.size() - 1);
        }
    }
}