Data Structures Explorer

Array

A fixed sequence of elements stored in contiguous memory. Think of it like a row of numbered boxes — you can jump to any box instantly using its index.

Random Access O(1) Insert/Delete O(n) Fixed Size

Interactive Array — click a cell to highlight, or add/remove values

Click a cell to inspect it.

Access by index

O(1)

Instant! Memory address = start + (index × size)

Search (unsorted)

O(n)

May need to scan every element.

Real-world use

Images

Pixels in an image are stored as a flat array of color values.

Stack

Last In, First Out (LIFO). Like a stack of plates — you can only add or remove from the top. Push adds, pop removes the top item.

Push O(1) Pop O(1) Search O(n)

Stack Visualizer — LIFO order

Stack is empty. Push something!

Real-world uses

Browser History

Each page you visit is pushed. Back button pops the stack.

Undo / Redo

Every action is pushed. Undo pops the last action.

Function Calls

Your CPU uses a call stack to track nested function calls.

Queue

First In, First Out (FIFO). Like a checkout line — whoever arrived first gets served first. Enqueue adds to the back, dequeue removes from the front.

Enqueue O(1) Dequeue O(1) Search O(n)

Queue Visualizer — FIFO order (left = front)

Queue is empty. Enqueue something!

Printer Queue

🖨️ Print Jobs

Jobs print in the order they were sent — first in, first out.

Keyboard Buffer

⌨️ Key Events

Keystrokes queue up and process in order.

vs Stack

FIFO≠LIFO

Queue removes from front. Stack removes from top (same end).

Linked List

A chain of nodes where each node holds a value and a pointer to the next. Unlike arrays, nodes don't need to be in contiguous memory — they're linked by references.

Insert at head O(1) Access by index O(n) Search O(n)

Linked List Visualizer — each box shows [value | next→]

Add a node to start building.

Array vs Linked List

Dynamic

Linked lists grow/shrink easily. Arrays need resizing.

Memory layout

Scattered

Nodes can be anywhere in memory, connected by pointers.

Real-world use

Music Queue

A playlist where each song points to the next one.

Binary Tree

A hierarchical structure where each node has at most two children (left & right). Binary Search Trees (BST) keep smaller values left, larger right — making search lightning fast.

Search O(log n) Insert O(log n) Worst case O(n)

Binary Search Tree — insert numbers, watch it self-organize

Insert a number to start building a BST.

BST Rule

Left < Root < Right

At every node, left subtree has smaller values, right has larger.

Why O(log n)?

Halving

Each step eliminates half the remaining nodes — like binary search.

Real-world use

File Systems

Folders and files form a tree hierarchy on your computer.