$(2$Marks$)$

The following algorithm takes as input an array, and returns the array with all the duplicate elements removed. For example, if the input array is $\{77,78,7864,39,78,39\},$ the algorithm returns $\{77,78,64,39\}.$

$S=$ new empty set

$D=$ new erpoty dynamic array

for every element $x$ in input array

if not S$.$member$($x$)$ then

S$.$insert$($x$)$

D$.$append $(x)$

return D

What is the big$-$O complexity of this algorithm, if the set is implemented as