Given a set, find XOR of the XOR's of all subsets.

The question is to find XOR of the XOR's of all subsets. i.e if the set is {1,2,3}. All subsets are : [{1}, {2}, {3}, {1, 2}, {1, 3}, {2, 3}, {1, 2, 3}]. Find the XOR of each of the subset and then find the XOR of every subset result.
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This is a very simple question to solve if we get the first step (and only step) right. The solution is XOR is always 0 when n > 1 and Set[0] when n is 1. 
 

Output: 

XOR of XOR's of all subsets is 0

Time Complexity: O(1)

Auxiliary Space: O(1)

Related Problem : 
Sum of XOR of all possible subsets
How does this work? 
The logic goes simple. When we apply XOR on all the subsets of a set, we can use the commutative and associative property of XOR which reduces the problem to finding XOR result of each element that depends on the total number of occurrences of each element. Eg. XOR([{1}, {2}, {3}, {1, 2}, {1, 3}, {2, 3}, {1, 2, 3}]) = XOR(XOR(1,1,1,1), XOR(2,2,2,2), XOR(3,3,3,3), XOR(4,4,4,4))

Let us consider n'th element, it can be included in the power set of remaining (n-1) elements. The number of subsets for (n-1) elements is equal to 2^(n-1) which is always even when n>1. Thus, in the XOR result, every element is included even number of times and XOR of even occurrences of any number is 0.