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LeetCode Solutions

78. Subsets

Time: $O(2^n)$

Space: $O(n \cdot 2^n)$

			


class Solution {
 public:
  vector<vector<int>> subsets(vector<int>& nums) {
    vector<vector<int>> ans;
    dfs(nums, 0, {}, ans);
    return ans;
  }

 private:
  void dfs(const vector<int>& nums, int s, vector<int>&& path,
           vector<vector<int>>& ans) {
    ans.push_back(path);

    for (int i = s; i < nums.size(); ++i) {
      path.push_back(nums[i]);
      dfs(nums, i + 1, move(path), ans);
      path.pop_back();
    }
  }
};




			


class Solution {
  public List<List<Integer>> subsets(int[] nums) {
    List<List<Integer>> ans = new ArrayList<>();
    dfs(nums, 0, new ArrayList<>(), ans);
    return ans;
  }

  private void dfs(int[] nums, int s, List<Integer> path, List<List<Integer>> ans) {
    ans.add(new ArrayList<>(path));

    for (int i = s; i < nums.length; ++i) {
      path.add(nums[i]);
      dfs(nums, i + 1, path, ans);
      path.remove(path.size() - 1);
    }
  }
}




			


class Solution:
  def subsets(self, nums: List[int]) -> List[List[int]]:
    ans = []

    def dfs(s: int, path: List[int]) -> None:
      ans.append(path)

      for i in range(s, len(nums)):
        dfs(i + 1, path + [nums[i]])

    dfs(0, [])
    return ans