Subsets(lintcode 17)

Description

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

Notice:

Elements in a subset must be in non-descending order.
The solution set must not contain duplicate subsets.

Example

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

[
  [3],
  [1],
  [2],
  [1,2,3],
  [1,3],
  [2,3],
  [1,2],
  []
]

Interface

class Solution {
    /**
     * @param S: A set of numbers.
     * @return: A list of lists. All valid subsets.
     */
    public ArrayList<ArrayList<Integer>> subsets(int[] nums) {
        // write your code here
    }
}

Solution

class Solution {
    /**
     * @param S: A set of numbers.
     * @return: A list of lists. All valid subsets.
     */
    public ArrayList<ArrayList<Integer>> subsets(int[] nums) {
        // write your code here
        ArrayList<ArrayList<Integer>> result = new ArrayList<ArrayList<Integer>>();
        int n = nums.length;
        Arrays.sort(nums);

        for (int i = 0; i < (1 << n); ++i) {
            ArrayList<Integer> list = new ArrayList<Integer>();
            for (int j = 0; j < n; ++j) {
                if ((i & (1 << j)) != 0) {
                    list.add(nums[j]);
                }
            }
            result.add(list);
        }

        return result;
    }
}