CODE

public class Solution {
  public List<List<int>> Subsets(int[] nums) {
    List<List<int>> subsets = new List<List<int>>();

    List<int> subset = new List<int>();
    subsets.Add(subset);

    for (int i = 0; i < nums.Length; i++)
    {
      List<int> singular = new List<int>();
      singular.Add(nums[i]);
      subsets.Add(singular);
    }

    int s_size = 1;

    while (s_size < nums.Length)
    {
      int ssCount = subsets.Count;
      int ss_start = 0;
      while (subsets[ss_start].Count < s_size)
      {
        ss_start++;
        continue;
      }

      for (int i = ss_start; i < ssCount; i++)
      {
        for (int j = 1; j < nums.Length; j++)
        {
          if (!subsets[i].Contains(nums[j]))
          {
            List<int> new_subset = new List<int>(subsets[i]);
            new_subset.Add(nums[j]);
            new_subset.Sort();
            if (!checkIfExists(subsets, new_subset))
              subsets.Add(new_subset);
          }
        }
      }
      s_size++;
    }
    return subsets;
  }

  bool checkIfExists(List<List<int>> subsets, List<int> subset)
  {
    for (int i = 0; i < subsets.Count; i++)
    {
      bool found = true;
      if (subsets[i].Count != subset.Count)
        continue;
      for (int j = 0; j < subsets[i].Count; j++)
      {
        if (subset[j] != subsets[i][j])
          found = false;
      }
      if (found)
        return true;
    }
    return false;
  }