Doubly Linked Lists and Applications

DSA, Database System & Operating System — Data Structure, Lists, Linked Lists and Trees, NEC licence examination syllabus (Nepal Engineering Council).

Doubly Linked Lists and Applications

The extra "previous" pointer opens up patterns a singly linked list simply can't do.

Because each node in a doubly linked list can reach both its neighbours, you can delete a node in O(1) time GIVEN just a pointer to it (no need to separately track "the node before it," unlike singly linked lists).

🖥️ Real Applications

Browser historyForward/back navigation needs traversal in BOTH directions.

Undo/redo systemsMove backward (undo) or forward (redo) through a sequence of actions.

💡 One-liner: "Why is deleting a given node O(1) in a doubly linked list, but O(n) in a singly linked list (without a separate previous pointer)?" → Doubly linked lists can directly access the previous node to relink; singly linked lists must traverse from the head just to FIND the previous node first.

Syllabus points

Doubly linked list operations & uses

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