Subsets II

1. Title

Subsets II

2.   Http address

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

3. The question

Given a collection of integers that might contain duplicates, nums, 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 nums = [1,2,2], a solution is:

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

4. My code (AC)

public static void helper(int [] nums, int start,List<Integer> sub_set, List<List<Integer>> res_set)
    {
        int len = nums.length;
        if ( start > len)
            return;
        res_set.add(new ArrayList<Integer>(sub_set));
        for(int i = start ; i < len; i++)
        {
            if ( i != start && nums[i] == nums[i-1])
                continue;
            sub_set.add(nums[i]);
            helper(nums, i + 1, sub_set, res_set);
            sub_set.remove(sub_set.size() - 1);
        }
    }
    
    // Accepted
    public static List<List<Integer>> subsetsWithDup(int[] nums) {
        
        Arrays.sort(nums);
        
        List<List<Integer>> res_set = new ArrayList<List<Integer>>();
        helper(nums, 0, new ArrayList<Integer>(), res_set);
        return res_set;
    }