Example 2:

Input:
nums = [0]
Output:
[[],[0]]

This is follow up from: Subsets

Solution

Method 1 - Backtracking

In this case we have to sort the array, as it is easy to compare if elements are duplicate by just looking at adjacent places.

Thought Process 1 - Focus One Element at Each Level

Each recursion level focuses on one element, we need to decide choose or not choose this element. (Every level split into 2 branches.)

public List<List<Integer>> subsetsWithDup(int[] nums) {
	Arrays.sort(nums);
	List<List<Integer>> ans = new ArrayList<>();
 
	dfs(nums, 0, ans, new ArrayList<>());
 
	return ans;
}
 
public void dfs(int[] nums,

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