【LeetCode】 Subsets

Given a set of distinct integers, S, return all possible subsets.

Note:

• Elements in a subset must be in non-descending order.
• The solution set must not contain duplicate subsets.

For example,
If S = [1,2,3], a solution is:

[
  [3],
  [1],
  [2],
  [1,2,3],
  [1,3],
  [2,3],
  [1,2],
  []
]

Discuss

java code :

public class Solution {
    public ArrayList<ArrayList<Integer>> subsets(int[] S) {
        // IMPORTANT: Please reset any member data you declared, as
        // the same Solution instance will be reused for each test case.
        ArrayList<ArrayList<Integer>> res = new ArrayList<ArrayList<Integer>>();
		res.add(new ArrayList<Integer>());
		if(S.length ==0)
			return res;
		Arrays.sort(S);
		ArrayList<Integer> tmp = new ArrayList<Integer>();
		for(int i = 1; i <= S.length; i++)
		{
			tmp.clear();
			recursion(res,tmp,i,S,0);
		}
		return res;
    }
    public void recursion(ArrayList<ArrayList<Integer>> res, ArrayList<Integer> tmp, int k, int[] S, int dp)
	{
		if(k == tmp.size())
		{
			res.add(new ArrayList<Integer>(tmp));
			return ;
		}
		for(int i = dp; i < S.length; i++)
		{
			tmp.add(S[i]);
			recursion(res,tmp,k,S,i+1);
			tmp.remove(tmp.size() - 1);
		}
	}
}