Subsets

06/28/2016 Array Backtracking Bit Manipulation

Question
Solution

Question

Given a set of distinct integers, nums, return all possible subsets.

Note: The solution set must not contain duplicate subsets.

For example,

If nums = [1,2,3], a solution is:
[
  [3],
  [1],
  [2],
  [1,2,3],
  [1,3],
  [2,3],
  [1,2],
  []
]

Solution

Result: Accepted Time: 8 ms

Here should be some explanations.

class Solution {
public:
    vector<vector<int>> subsets(vector<int>& nums) {
        vector<vector<int>> ans;
        sort(nums.begin(),nums.end());
        int len = 1<<nums.size();
        for(int i = 0 ; i < len; i++ )
            {
                int tmp = i;
                vector<int> vec;
                for(int j = 0;tmp;j++ )
                    {
                        if(tmp & 1)
                            vec.push_back(nums[j]);
                        tmp >>= 1;
                    }
                ans.push_back(vec);
            }
        return ans;
    }
};

Complexity Analytics

Time Complexity: $O(2^n)$
Space Complexity: $O(2^n)$