✅ Comparison Between Array and Linked List (BCA Exam Answer)
| Feature | Array | Linked List |
|---|---|---|
| Definition | Collection of elements stored in contiguous memory locations | Collection of nodes stored in non-contiguous memory connected using pointers |
| Memory Allocation | Static (fixed size, mostly) | Dynamic (size can grow/shrink at runtime) |
| Accessing Elements | Direct / Random access using index A[i] | Sequential access (must traverse from head) |
| Insertion | Difficult (requires shifting) | Easy (only pointer changes) |
| Deletion | Difficult (requires shifting) | Easy (only pointer changes) |
| Memory Wastage | Possible (if declared size is large) | No wastage (uses memory as required) |
| Extra Memory | No extra memory required | Extra memory needed for pointer (next) |
| Time for Searching | Faster (index based access) | Slower (must traverse node by node) |
| Implementation | Simple | Slightly complex (pointers required) |
| Best Used When | Fixed size data and frequent access | Dynamic size data and frequent insertion/deletion |
✅ Conclusion (2–3 Lines)
Arrays provide fast access using indexing but have fixed size and insertion/deletion is costly.
Linked lists are dynamic and support easy insertion/deletion but require extra memory and have slower access.
✅ Comparison of Arrays and Linked Lists
✅ Introduction
Both Array and Linked List are linear data structures used to store multiple elements.
But they differ in memory allocation, access method, performance, and applications.
✅ 1. Memory Storage Location
✅ Array
- Array elements are stored in contiguous (continuous) memory locations.
- Each element is placed next to the previous element.
📌 Example:
A[0] A[1] A[2] A[3]
1000 1004 1008 1012 (continuous memory)
✅ Because of contiguous memory, arrays support direct indexing.
✅ Linked List
- Linked list nodes are stored in non-contiguous (random) memory locations.
- Nodes are connected using pointers/links.
📌 Example:
HEAD → [10|•] → [20|•] → [30|NULL]
2000 5000 3200 (different memory)
✅ Nodes can be anywhere in memory, but pointers maintain the order.
✅ 2. Size (Static vs Dynamic)
✅ Array
- Size is generally fixed at the time of declaration.
- Cannot increase or decrease easily.
✅ Example:
int A[10];
📌 Problem:
- If we need more than 10 elements → overflow
- If we use only 5 elements → memory wastage
✅ Linked List
- Size is dynamic, it can grow or shrink during runtime.
- Memory is allocated whenever required.
✅ Example: Nodes created using malloc() in C.
📌 Benefit:
- No fixed limit
- Better memory utilization
✅ 3. Accessing Elements (Random vs Sequential)
✅ Array
- Supports Random Access
- Any element can be accessed directly using index.
✅ Example:
A[5]
📌 Time for access:
✅ O(1)
✅ Linked List
- Does not support direct access.
- To reach a node, traversal starts from HEAD.
✅ Example:
To access 5th node, we must pass nodes 1 → 2 → 3 → 4 → 5
📌 Time for access:
✅ O(n)
✅ 4. Insertion Operation
✅ Array
Insertion is difficult because it requires shifting elements.
📌 Example:
Insert 25 at position 2 in:10 20 30 40
Shifting required:10 _ 20 30 40
Final:10 25 20 30 40
✅ Time complexity:
- Worst case: O(n)
✅ Linked List
Insertion is easy because only pointer changes are needed.
📌 Example:
Insert 25 after 20:
10 → 20 → 30 → 40
After insertion:
10 → 20 → 25 → 30 → 40
✅ No shifting required
✅ Time complexity:
- O(1) (if position pointer is known)
✅ 5. Deletion Operation
✅ Array
Deletion requires shifting to fill gap.
📌 Example:
Delete 20 from:10 20 30 40
After deletion:10 30 40 (shifting required)
✅ Time complexity:
- Worst case: O(n)
✅ Linked List
Deletion is easy by changing links.
📌 Example:
Delete 20:
10 → 20 → 30 → 40
After deletion:
10 → 30 → 40
✅ No shifting required
✅ Time complexity:
- O(1) (if node location is known)
✅ 6. Memory Utilization
✅ Array
✅ Advantages:
- No extra memory needed (only data stored)
❌ Disadvantages:
- Memory wastage possible due to fixed size
✅ Linked List
✅ Advantages:
- Uses memory as needed (dynamic)
❌ Disadvantages:
- Extra memory is needed for storing pointer/address.
📌 Node structure:
[DATA | NEXT]
✅ So linked list uses more memory per element than array.
✅ 7. Searching Performance
✅ Array
- Linear search: O(n)
- Binary search (if sorted): O(log n) ✅
✅ Binary search is possible because array supports indexing.
✅ Linked List
- Searching is generally O(n)
- Binary search is not efficient because no direct indexing exists.
✅ 8. Implementation Complexity
✅ Array
✅ Easy to implement
✅ Simple operations using indexing
✅ Linked List
❌ Slightly complex
Needs:
- pointers
- dynamic memory allocation
- node creation & linking
✅ 9. Applications (Where Used)
✅ Array is Best Used When:
✅ Data size is fixed
✅ Fast access is required
✅ Less insertion/deletion needed
📌 Examples:
- Marks list
- Student roll numbers
- Matrix operations
✅ Linked List is Best Used When:
✅ Data size changes frequently
✅ Insertions/deletions are frequent
✅ Memory efficiency needed
📌 Examples:
- Stack and Queue implementation
- Music playlist
- Browser history
- Polynomial operations
✅ Summary Table (Very Important)
| Feature | Array | Linked List |
|---|---|---|
| Memory Location | Contiguous | Non-contiguous |
| Size | Fixed | Dynamic |
| Access | Random (Direct) | Sequential |
| Insertion | Slow (shifting) | Fast (pointer change) |
| Deletion | Slow (shifting) | Fast (pointer change) |
| Extra Memory | No | Yes (pointer needed) |
| Search | Faster (Binary search possible) | Slower |
| Implementation | Easy | Complex |
✅ Conclusion
Arrays are best for fast access and fixed-size data, but insertion and deletion are slow due to shifting.
Linked lists are best for dynamic memory and frequent insertion/deletion, but they require extra memory and are slower for accessing elements.