Sort the given biotonic doubly linked list. A biotonic doubly linked list is a doubly linked list which is first increasing and then decreasing. A strictly increasing or a strictly decreasing list is also a biotonic doubly linked list.
Approach: Find the first node in the list which is smaller than its previous node. Let it be current. If no such node is present then list is already sorted. Else split the list into two lists, first starting from head node till the current’s previous node and second starting from current node till the end of the list. Reverse the second doubly linked list. Refer this post. Now merge the first and second sorted doubly linked list. Refer merge procedure of this post. The final merged list is the required sorted doubly linked list.
Original Doubly linked list: 2 5 7 12 10 6 4 1 Doubly linked list after sorting: 1 2 4 5 6 7 10 12
Time Complexity: O(n)
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