public void dosomething$()\{$

ArrayList $$ Integer $>$ set $=$ new ArrayList $$ Integer $>()$ Timeleft

Stack tempStack $=$ new Stack$($arr$.$ length$)$;

while $(!$isEmpty $())\{$

int current $=$pop$()$;

if $(!$ set.contains$($current$))\{$

set.add $($current$)$;

tempStack.push$($current$)$;

$\}$

$\}$

while $(!$tempStack.isEmpty $())\{$

push $($tempStack$.$pop$())$;

$\}$

$\}$

A$.$ Remove duplicates from a given stack.

B$.$ Sort the elements of the stack in descending order.

C$.$ Reverse the elements of a stack.

D$.$ Rotate the stack elements to the right direction.