LeetCode -- Subsets II

LeetCode -- Subsets II
Description:


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], a solution is:


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


Ideas:
It is also a backtracking question.
This question is very similar to Combination Sum.


Note that deduplication uses hash to store the ascending key.


Implementation Code:

public class Solution {    public IList
 
  > SubsetsWithDup(int[] nums)     {    Dictionary
  
   > result = new Dictionary
   
    >();    Travel(nums.ToList() ,new List
    
     (), 0, result);        return result.Values.ToList();    }private void Travel(IList
     
       nums, IList
      
        arr, int index, Dictionary
       
        > result){var k = K(ref arr);if(!result.ContainsKey(k)){result.Add(k, new List
        
         (arr));}for(var i = index ;i < nums.Count; i++){arr.Add(nums[i]);Travel(nums, arr, i + 1, result);arr.Remove(nums[i]);}}private string K(ref IList
         
           arr){arr = arr.OrderBy(x=>x).ToList();return string.Join(,, arr);}}