【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);

		}

	}

}