Linked lis deepcopy O(1)

problem='https://practice.geeksforgeeks.org/problems/clone-a-linked-list-with-next-and-random-pointer/1'
class Solution:
    def copyList(self, head):
        cur=head
        while cur:
            t=cur.next#next node
            cp=Node(cur.data)#copy node
            cur.next=cp#setting up copied nodes
            cp.next=t
            cur=cp.next
        cur=head
        while cur:#arrange random pointers
            cur.next.arb=cur.arb.next if cur.arb else None
            cur=cur.next.next if cur.next else None
        cur=head
        t=ans=head.next
        while cur:#setup ans chain
            cur.next=cur.next.next if cur.next else None
            t.next=t.next.next if t.next else None
            cur,t=cur.next,t.next
        return ans