Subsets II

Java

public class Solution {
    /**
     * @param nums: A set of numbers.
     * @return: A list of lists. All valid subsets.
     */
    public List<List<Integer>> subsetsWithDup(int[] nums) {
        // write your code here
        List<List<Integer>> result = new ArrayList<>();
        List<Integer> path = new ArrayList<>();
        Arrays.sort(nums);
        dfs(nums, result, path, 0, -1);
        return result;
    }
    
    private void dfs(int[] nums, List<List<Integer>> result, List<Integer> path, int index, int lastSelected) {
        if (index == nums.length) {
            result.add(new ArrayList<>(path));
            return;
        }
        
        // not select
        dfs(nums, result, path, index + 1, lastSelected);
        
        
        // select
        if (index > 0 && nums[index] == nums[index - 1] && lastSelected != index - 1) {
            return;
        }
        path.add(nums[index]);
        dfs(nums, result, path, index + 1, index);
        path.remove(path.size() - 1);
    }
}