LeetCode Print all subsets of a set

Reference:

https://leetcode.com/problems/subsets/

Solution References:

http://bangbingsyb.blogspot.com/2014/11/leetcode-subsets-i-ii.html

Above solution has clear implementations in  C++

Solution in Java

package subsets;

import java.util.Collections;

import java.util.List;

import java.util.ArrayList;

public class Solution {

public static void main (String args[])

{

Solution s1 = new Solution();

ArrayList<Integer> a = new ArrayList<Integer>();

a.add(1);a.add(2);a.add(3);

System.out.println(s1.subsets(a));

}

public ArrayList<ArrayList<Integer>> subsets(ArrayList<Integer> a) 

{
  //we sort the list in order to be the output in lexicographically sorted order

Collections.sort(a);

ArrayList<ArrayList<Integer>> res = new ArrayList<ArrayList<Integer>>();

ArrayList<Integer> temp = new ArrayList<Integer>();

res.add(new ArrayList<Integer>());

combination(a,res,temp,0);

return res;

   

}

static void combination(ArrayList<Integer> a,ArrayList<ArrayList<Integer>>res,ArrayList<Integer> temp,int index)

{

for(int i = index;i<a.size();++i)

{

temp.add(a.get(i));
//we make deep copy of temp list since java by default will do a shallow copy hence it will remove elements from result list .

res.add(new ArrayList(temp));

combination(a, res, temp,i+1);

temp.remove(temp.size()-1);

}

}

}