Finding the sum of all subsets of a given set

Question

Suggest an algorithm for finding the sum of all subsets of a set.

For example, if k=3 and the subsets are {1},{2},{3},{1,2},{1,3},{2,3},{1,2,3}

Answer 1

Each element appears the same number of times, which happens to be 2^n-1 where n is number of elements. So the answer is: count sum of elements in the set and multiply it by 2^n-1