ds-lab-codes/QueueInLL.c

#include<stdio.h>
#include<stdlib.h>

typedef struct node{
    int data;
    struct node* next;
}Node;

Node* front = NULL;
Node* rear = NULL;

void enqueue(int value)
{   
    Node* newnode = (Node*)malloc(sizeof(Node));

    if(!newnode){
        fprintf(stderr, "Memory allocation failed\n");
        exit(1);
    }

    newnode->data = value;
    newnode->next = NULL;

    if(front == NULL){
        rear = front = newnode;
    }else{
        rear->next = newnode;
        rear = newnode;
    }
    printf("added %d onto rear\n", value);


}

int dequeue(){
    Node* temp = front;
    int item;
    if(front == NULL){
        printf("stack is empty");
        return -1;
    }
    item = temp->data;
    front = front->next;
    free(temp);

    if(front== NULL){
        rear = NULL;
    }
    return item;
}

void display(){
    Node* temp = front;
    if(front == NULL){
        printf("Stack is empty");
        return;
    }

    while(temp!=NULL){
        printf("%d->",temp->data);
        temp = temp->next;

    }
    printf("NULL\n");
}
int main(){
    int choice,value;
    while(1){
        printf("\n---queue menu---");
        printf("\n1. enqueue");
        printf("\n2. dequeue");
        printf("\n3. display");
        printf("\n4. exit");
        printf("\nEnter your choice: ");
        scanf("%d", &choice);

        switch(choice){
            case 1: printf("Enter item to be added: ");
                    scanf("%d", &value);
                    enqueue(value);
                    break;
            case 2: value = dequeue();
                    if(value!=-1)
                    printf("popped %d", value);
                    break;
            case 3: display();
                    break;
            case 4: printf("exiting\n");
                    exit(0);
            default: 
                    printf("enter valid choice bruh");


        }

    }
    return 0;
}