Question 1 : For each of the Singly Linked List, Circularly Singly Linked List, Doubly Linked List, Circularly Doubly Linked List, write one application that is exclusively suitable for that list. For example, X may be an application for whose implementation, only Circularly Singly Linked List is suitable and others are not suitable. Justify your answer.

1. Singly Linked List (SLL)

Application: Implementation of a simple Undo feature with limited backward access (e.g., text editor undo stack)

Justification:

• Undo operations proceed in one direction only (latest action undone first).
• Only forward traversal is required from the top of the list.
• Singly Linked List requires less memory (only one pointer per node).

Why others are not suitable:

• Doubly Linked List: Extra backward pointer wastes memory.
• Circular Lists: No need for circular traversal; may complicate termination conditions.

Hence, Singly Linked List is the most efficient and suitable choice.

2. Circular Singly Linked List (CSLL)

Application:  Round-Robin CPU Scheduling

Justification:

• After the last process, CPU must return to the first process automatically.
• Circular structure allows continuous traversal without NULL checks.
• Each process gets CPU time in a cyclic manner.

Why others are not suitable:

• Singly Linked List: Requires jumping back to the head explicitly.
• Doubly Linked List: Backward traversal is unnecessary.
• Circular Doubly Linked List: Extra memory overhead not required.

Thus, Circular Singly Linked List is ideal for round-robin scheduling.

3. Doubly Linked List (DLL)

Application: Browser Backward and Forward Navigation (History List)

Justification:

• User must move both backward and forward between pages.
• Doubly Linked List supports bi-directional traversal efficiently.
• Deletion of current page is easier using previous pointer.

Why others are not suitable:

• Singly Linked List: Cannot move backward efficiently.
• Circular Lists: Browsing history is linear, not cyclic.

Therefore, Doubly Linked List is best suited for browser navigation.

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4. Circular Doubly Linked List (CDLL)

Application: Music Playlist with Next and Previous Navigation (Repeat Mode ON)

Justification:

• Playlist must repeat from last song to first and vice versa.
• User can move next or previous at any point.
• Circularity ensures continuous playback, and double links allow easy navigation.

Why others are not suitable:

• Singly Lists: Cannot move backward.
• Non-circular Lists: Playlist would stop at the end.
• Circular Singly List: Previous song navigation is inefficient.

 Hence, Circular Doubly Linked List is the most suitable choice.