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#0Doubly Linked List Visualizer
See how previous and next pointers support insertion, deletion, search, and bidirectional traversal in an animated doubly linked list.
Current status: Ready to link nodes in both directions.
Pointer playground
Doubly Linked List Visualizer
Every node knows its neighbor on both sides. Follow the cyan next links forward or the fuchsia prev links backward.
Build your list
Add or remove nodes
Insert
Remove
Explore
Memory view
Two links per node, twice the direction
next prev
HEADprev: null
Head node
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#1Node at index 1
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#2Node at index 2
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#3Node at index 3
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#4Node at index 4
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#5Tail node
TAILnext: null
Traversal output
Visited nodes
Run a forward or backward traversal to reveal the visit order.
Under the hood
Pointer update sketch
Choose an operation, then open its concise Java pointer-update sketch. The active node in the memory view shows where the action happened.
Why use a doubly linked list?
A doubly linked list stores a prev pointer and a next pointer in every node. That extra pointer costs memory, but it makes reverse traversal natural and lets a known node be unlinked without first finding its predecessor.
Head / tail insert
O(1)
Search
O(n)
Reverse traversal
O(n)
Concept guide
Review the mental model, tradeoffs, and practical use cases after you experiment.
Doubly Linked List Complete Info Card
BidirectionalTwo Pointers
A Doubly Linked List consists of nodes with data, a next pointer, and a prev pointer, enabling traversal in both directions. Each node points to both its successor and predecessor.
Operations & Complexities
Insert at Head
Add new node at beginning
Insert at Tail
Add new node at end (with tail pointer)
Delete at Head
Remove first node
Delete at Tail
Remove last node
Insert at Position
Traverse to position then insert
Delete by Value
Find then remove node
Search Forward
Traverse head to tail
Search Backward
Traverse tail to head
Vs. Singly Linked List
| Feature | Singly | Doubly |
|---|---|---|
| Traversal Direction | Forward only | Both directions |
| Node Memory | 1 pointer (next) | 2 pointers (prev, next) |
| Delete Operations | O(n) for tail deletion | O(1) for head/tail |
| Memory Overhead | Lower | Higher (extra pointer per node) |
Memory Visualization
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Data
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Practical Applications
Browser History
Forward/backward navigation
Music Playlist
Bidirectional navigation
Undo/Redo Functionality
Maintaining state history
Blockchain
Linking blocks bidirectionally
Variations
Circular Doubly Linked List
Head.prev points to tail, tail.next points to head
Multi-Level Doubly Linked List
Nodes may have child lists (like file systems)
XOR Linked List
Memory-optimized using XOR of addresses
Implementation Considerations
When to Use
- •Need bidirectional traversal
- •Frequent tail operations
- •Implementing undo/redo
When to Avoid
- •Memory-constrained environments
- •Only forward traversal needed
- •Frequent random access
Pro Tip: Always maintain both next and prev pointers consistently during modifications to prevent broken links.
BidirectionalO(1) head/tail opsMore memory