Types of LinkedList
Linked lists come in different variations based on how nodes are connected and how traversal is performed. The three main types of linked lists are:
- Singly Linked List
- Doubly Linked List
- Circular Linked List
Each type has different properties and is used in different scenarios.
1. Singly Linked List
A Singly Linked List (SLL) is the simplest form of a linked list.
- Each node contains data and a pointer to the next node.
- Traversal is one-directional, meaning we can only move forward through the list.
- The last node’s pointer is NULL, indicating the end of the list.
Characteristics
✅ Simple and easy to implement.
✅ Uses less memory than doubly linked lists.
✅ Efficient for sequential traversal and insertions at the beginning.
❌ Backward traversal is not possible.
❌ Deletion of a node requires modifying previous node’s pointer.
Node Structure for Singly Linked List
// Node structure for Singly Linked List
class ListNode {
int val; // Data stored in the node
ListNode next; // Pointer to the next node
ListNode(int val) {
this.val = val;
this.next = null;
}
}
2. Doubly Linked List
A Doubly Linked List (DLL) allows two-way traversal.
- Each node contains data, a pointer to the next node, and a pointer to the previous node.
- This allows movement both forward and backward.
Characteristics
✅ Allows both forward and backward traversal.
✅ More flexible than singly linked lists.
✅ Efficient deletion since we have a reference to the previous node.
❌ Requires extra memory due to the additional pointer.
❌ More complex to implement than singly linked lists.
Node Structure for Doubly Linked List
// Java: Doubly Linked List Node
class DLNode {
int val;
DLNode prev, next; // Pointers to previous and next nodes
DLNode(int val) {
this.val = val;
this.prev = this.next = null;
}
}
3. Circular Linked List
A Circular Linked List (CLL) is a variation where:
- The last node points back to the first node, forming a loop.
- Can be singly or doubly circular.
Characteristics
✅ No NULL pointers; last node connects to first.
✅ More efficient in circular applications (e.g., Round Robin scheduling).
✅ Useful in buffered data structures like audio/video streaming.
❌ More complex traversal due to looping nature.
Comparison of Linked List Types
| Feature | Singly Linked List | Doubly Linked List | Circular Linked List |
|---|---|---|---|
| Direction | One-way | Two-way | Can be one-way or two-way |
| Memory Usage | Lower | Higher (extra pointer) | Similar to singly |
| Traversal | Forward only | Forward & backward | Loops continuously |
| Usage | Simple lists | Complex operations | Circular applications |
Next, we will implement linked lists with insertion and deletion operations!
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