DSA Linked Lists in Memory

DSA Linked Lists in Memory – How Nodes Are Stored & Connected

(Addresses • Pointers • Comparison with Arrays)

Understanding how linked lists are stored in memory is crucial for DSA, pointers, and interviews.
This topic explains what actually happens in RAM, not just the theory.

1️⃣ How Data is Stored in Memory (Quick Recap)

• Memory (RAM) is divided into small blocks

• Each block has a unique address

• Variables store values

• Pointers store addresses

2️⃣ Linked List in Memory – Core Idea

A Linked List is stored as:

• Independent nodes

• Nodes are not stored contiguously

• Each node contains:

  • Data

  • Pointer (address of next node)

📌 Nodes can be anywhere in memory.

3️⃣ Singly Linked List – Memory Representation

Logical View

Memory View

📌

• next stores the address of the next node

• Order is maintained via links, not memory position

4️⃣ Why Linked Lists Are Not Contiguous

• Nodes are creating using dynamic memory allocation

  • new (C++)

  • malloc() (C)

• OS allocates first free memory block

• Hence, nodes may be scatter in memory

5️⃣ Pointer Role in Linked List

Each node contains a pointer:

• data → stores value

• next → stores address of next node

📌 Without pointers, linked lists cannot exist.

6️⃣ Traversing a Linked List in Memory

To traverse:

1. Start with head pointer

2. Read data

3. Jump to next address

4. Repeat until NULL

📌 CPU follows addresses step-by-step.

7️⃣ Doubly Linked List – Memory Representation

Each node stores two addresses:

Example

✔ Forward traversal
✔ Backward traversal
❌ Extra memory for prev pointer

8️⃣ Circular Linked List in Memory

Last node points back to head:

📌 No NULL pointer
📌 Useful for round-robin tasks

9️⃣ Linked List vs Array (Memory Comparison)

🔟 Why Linked Lists Are Slower Than Arrays

Even though insertion is fast, access is slow because:

• No direct indexing

• CPU must follow multiple memory jumps

• Poor cache locality

📌 This is why arr[i] is faster than linked list traversal.

1️⃣1️⃣ Memory Overhead in Linked Lists

Each node stores:

• Data (e.g., 4 bytes)

• Pointer (4 or 8 bytes)

📌 Almost double memory usage compared to arrays.

1️⃣2️⃣ Common Interview Questions

Q1. Are linked list nodes stored contiguously?
👉 No

Q2. What does next pointer store?
👉 Address of next node

Q3. Why linked lists need more memory?
👉 Extra pointers

Q4. Why arrays are cache-friendly?
👉 Contiguous memory

✅ Final Summary

✔ Linked list nodes are scattering in memory
✔ Pointers connect nodes logically
✔ Order is maintaining by addresses
✔ Traversal follows pointers
✔ Extra memory overhead
✔ Important for pointer-based questions