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Basics & Data Structures

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Array Access

array[0..5]indexed access

Array

Stack

Queue

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Sorting

Trees

Graphs

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Beginner Friendly

Queue: Array Implementation

Explore FIFO (First In, First Out) — enqueue at rear, dequeue at front, just like a real-world queue.

Interactive Operations

Array Implementation

O(1) Enqueue

Queue Visualization

FRONT = where elements leave | REAR = where elements arrive

Color Legend

Front elementOther elementsActiveCompletedError

Speed:

Max Size:

DEQUEUE (Front)

ENQUEUE (Rear)

Queue is empty — enqueue to begin

0 / 8

Size / Capacity

Empty

Status

Current Step

Use Enqueue, Dequeue, or Peek to begin visualization.

Complexity Analysis

O(1)

Enqueue

O(n)*

Dequeue

O(1)

Peek

O(n) Space

Fixed array allocation

*O(n) due to shifting. Circular array gives O(1) dequeue.

Queue Operations

Enqueue

Add element to the rear — increment rear pointer

Dequeue

Remove front element — shift array or advance front pointer

Peek / Front

View front element without removing it

FIFO Principle

Task Scheduling

OS processes tasks in arrival order

Print Queue

Documents print in the order they were sent

BFS Traversal

Explores graph level by level using a queue

Network Buffers

Packets queued and processed in order

Test Yourself

Q1/3

What does FIFO stand for?

Implementation

Python

class QueueArray:
    def __init__(self, max_size):
        self.array = [None] * max_size
        self.front = 0
        self.rear = -1
        self.size = 0
        self.max_size = max_size

    def enqueue(self, value):
        if self.size >= self.max_size:
            raise Exception("Queue Overflow")
        # Circular array: wrap rear pointer
        self.rear = (self.rear + 1) % self.max_size
        self.array[self.rear] = value
        self.size += 1
        return value

    def dequeue(self):
        if self.size <= 0:
            raise Exception("Queue Underflow")
        value = self.array[self.front]
        self.array[self.front] = None
        # Circular array: wrap front pointer
        self.front = (self.front + 1) % self.max_size
        self.size -= 1
        return value

    def peek(self):
        if self.size <= 0:
            raise Exception("Queue is Empty")
        return self.array[self.front]

    def is_empty(self):
        return self.size == 0

    def is_full(self):
        return self.size >= self.max_size

DSAverse

Basics & Data Structures

Loading Data Structures...

Array Access

array[0..5]indexed access

Array

Stack

Queue

Back to Basics

Beginner Friendly

Queue: Array Implementation

Explore FIFO (First In, First Out) — enqueue at rear, dequeue at front, just like a real-world queue.

Interactive Operations

Array Implementation

O(1) Enqueue

Queue Visualization

FRONT = where elements leave | REAR = where elements arrive

Color Legend

Front elementOther elementsActiveCompletedError

Speed:

Max Size:

DEQUEUE (Front)

ENQUEUE (Rear)

Queue is empty — enqueue to begin

0 / 8

Size / Capacity

Empty

Status

Current Step

Use Enqueue, Dequeue, or Peek to begin visualization.

Complexity Analysis

O(1)

Enqueue

O(n)*

Dequeue

O(1)

Peek

O(n) Space

Fixed array allocation

*O(n) due to shifting. Circular array gives O(1) dequeue.

Queue Operations

Enqueue

Add element to the rear — increment rear pointer

Dequeue

Remove front element — shift array or advance front pointer

Peek / Front

View front element without removing it

FIFO Principle

Task Scheduling

OS processes tasks in arrival order

Print Queue

Documents print in the order they were sent

BFS Traversal

Explores graph level by level using a queue

Network Buffers

Packets queued and processed in order

Test Yourself

Q1/3

What does FIFO stand for?

Implementation

Python

class QueueArray:
    def __init__(self, max_size):
        self.array = [None] * max_size
        self.front = 0
        self.rear = -1
        self.size = 0
        self.max_size = max_size

    def enqueue(self, value):
        if self.size >= self.max_size:
            raise Exception("Queue Overflow")
        # Circular array: wrap rear pointer
        self.rear = (self.rear + 1) % self.max_size
        self.array[self.rear] = value
        self.size += 1
        return value

    def dequeue(self):
        if self.size <= 0:
            raise Exception("Queue Underflow")
        value = self.array[self.front]
        self.array[self.front] = None
        # Circular array: wrap front pointer
        self.front = (self.front + 1) % self.max_size
        self.size -= 1
        return value

    def peek(self):
        if self.size <= 0:
            raise Exception("Queue is Empty")
        return self.array[self.front]

    def is_empty(self):
        return self.size == 0

    def is_full(self):
        return self.size >= self.max_size