Day 9.md

day	title	description
9	Data Structures	Covering Stacks, Queues, Circular Queues, their definitons,operations and implementaion

Day 9 - Data Structures

Data Structures

Definition

A data structure is a way of organizing and storing data in a computer so that it can be accessed and modified efficiently.

Types

• Primitive Data Structures: Basic structures like int, float, char, etc.
• Non-Primitive Data Structures: More complex structures like arrays, linked lists, stacks, queues, trees, graphs, etc.

Usage

Data structures are used to manage large amounts of data efficiently for various operations such as traversal, insertion, deletion, and searching.

Stacks

Definition

A stack is a linear data structure that follows the Last In First Out (LIFO) principle.

Implementation using Arrays

#include <stdio.h>
#define MAX 5

int stack[MAX], top = -1;

void push(int value) {
    if(top==MAX-1) {
        printf("Stack Overflow\n");
    }else{
        stack[++top] = value;
        printf("Inserted %d\n", value);
    }
}

void pop() {
    if(top==-1) {
        printf("Stack Underflow\n");
    }else{
        printf("Deleted %d\n",stack[top--]);
    }
}

void display() {
    if(top==-1) {
        printf("Stack is empty\n");
    }else{
        printf("Stack elements are:\n");
        for(int i=top;i>=0;i--) {
            printf("%d\n", stack[i]);
        }
    }
}

int main() {
    push(1);
    push(2);
    push(3);
    pop();
    pop();
    pop();
    pop();//underflow
    display();
    return 0;
}

Push Operation

The push operation adds an element to the top of the stack.

Pop Operation

The pop operation removes the top element from the stack.

Queues

Definition

A queue is a linear data structure that follows the First In First Out (FIFO) principle.

Implementation using Arrays

#include <stdio.h>
#define MAX 5

int queue[MAX], front=-1, rear=-1;

void enqueue(int value) {
    if(rear==MAX - 1) {
        printf("Queue Overflow\\n");
    } else {
        if(front==-1) front=0;
        queue[++rear]=value;
        printf("Inserted %d\\n", value);
    }
}

void dequeue() {
    if(front==-1 || front>rear) {
        printf("Queue Underflow\\n");
    } else {
        printf("Deleted %d\\n", queue[front++]);
        if(front > rear) front=rear=-1;//reset pointers
    }
}

void display() {
    if(front==-1) {
        printf("Queue is empty\\n");
    } else {
        printf("Queue elements are:\\n");
        for(int i=front; i<=rear;i++) {
            printf("%d\\n", queue[i]);
        }
    }
}

int main() {
    enqueue(1);
    enqueue(2);
    enqueue(3);
    dequeue();
    display();
    return 0;
}

Enqueue Operation

The enqueue operation adds an element to the end of the queue.

Dequeue Operation

The dequeue operation removes the front element from the queue.

Circular Queue

Definition

A circular queue is a linear data structure in which the last position is connected back to the first position to make a circle.

Implementation

#include <stdio.h>
#define MAX 5

int cqueue[MAX], front=-1, rear=-1;

void enqueue(int value) {
    if((front==0 && rear==MAX-1) || (rear+1)%MAX==front) {
        printf("Circular Queue Overflow\n");
    } else {
        if(front==-1) front=rear=0;
        else rear=(rear+1)%MAX;
        cqueue[rear]=value;
        printf("Inserted %d\n", value);
    }
}

void dequeue() {
    if(front==-1) {
        printf("Circular Queue Underflow\n");
    } else {
        printf("Deleted %d\n", cqueue[front]);
        if(front==rear) front=rear=-1;
        else front=(front+1) % MAX;
    }
}

void display() {
    if(front==-1) {
        printf("Circular Queue is empty\n");
    } else {
        printf("Circular Queue elements are:\n");
        int i=front;
        while(1) {
            printf("%d\n",cqueue[i]);
            if(i==rear) break;
            i=(i+1)%MAX;
        }
    }
}

int main() {
    enqueue(1);
    enqueue(2);
    enqueue(3);
    enqueue(4);
    dequeue();
    enqueue(5);
    display();
    return 0;
}

Operations

• Enqueue: Adds an element to the rear of the circular queue.
• Dequeue: Removes an element from the front of the circular queue.