#9 LeetCode ( Q: (90) Subsets II)

LeetCode 90 Subsets II, Coding Interview Question
Level : Medium
Challenge : 9/1000

Given a collection of integers that might contain duplicates, nums, return all possible subsets (the power set).

Note: The solution set must not contain duplicate subsets.

Example:

Input: [1,2,2]
Output:
[
  [2],
  [1],
  [1,2,2],
  [2,2],
  [1,2],
  []
]

Solution — Java

public class Solution {
    public List<List<Integer>> subsetsWithDup(int[] nums) {
        List<List<Integer>> res = new ArrayList<List<Integer>> ();
        List<Integer> item = new ArrayList<Integer>();
        if(nums.length==0||nums==null)
            return res;
        Arrays.sort(nums);
        for(int len = 1; len<= nums.length; len++)
               dfs(nums,0,len,item,res);
        res.add(new ArrayList<Integer>());
        return res;
    }
    public static void dfs(int[] nums, int start, int len, List<Integer> item,List<List<Integer>> res){
        if(item.size()==len){
            res.add(new ArrayList<Integer>(item));
            return;
        }
        for(int i=start; i<nums.length;i++){
            item.add(nums[i]);
            dfs(nums, i+1, len, item, res);
            item.remove(item.size()-1);
            while(i<nums.length-1&&nums[i]==nums[i+1])//skip duplicate element
                i++;
        }//for
    }
}

Goal : 9 / 10

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