Subsets - Implementation

Here is the implementation:

function subsets(nums):
    result = []
    backtrack(0, [])
    return result

function backtrack(index, current):
    if index == nums.length:
        result.append(copy of current)
        return

    // Include nums[index]
    current.append(nums[index])
    backtrack(index + 1, current)
    current.pop()

    // Exclude nums[index]
    backtrack(index + 1, current)

$O(n \cdot 2^n)$ time to generate all subsets and copy them. $O(n)$ space for recursion stack.