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/* Queue - Circular Array implementation in C++*/ | |
#include<iostream> | |
using namespace std; | |
#define MAX_SIZE 101 //maximum size of the array that will store Queue. | |
// Creating a class named Queue. | |
class Queue | |
{ | |
private: | |
int A[MAX_SIZE]; | |
int front, rear; | |
public: | |
// Constructor - set front and rear as -1. | |
// We are assuming that for an empty Queue, both front and rear will be -1. | |
Queue() | |
{ | |
front = -1; | |
rear = -1; | |
} | |
// To check wheter Queue is empty or not | |
bool IsEmpty() | |
{ | |
return (front == -1 && rear == -1); | |
} | |
// To check whether Queue is full or not | |
bool IsFull() | |
{ | |
return (rear+1)%MAX_SIZE == front ? true : false; | |
} | |
// Inserts an element in queue at rear end | |
void Enqueue(int x) | |
{ | |
cout<<"Enqueuing "<<x<<" \n"; | |
if(IsFull()) | |
{ | |
cout<<"Error: Queue is Full\n"; | |
return; | |
} | |
if (IsEmpty()) | |
{ | |
front = rear = 0; | |
} | |
else | |
{ | |
rear = (rear+1)%MAX_SIZE; | |
} | |
A[rear] = x; | |
} | |
// Removes an element in Queue from front end. | |
void Dequeue() | |
{ | |
cout<<"Dequeuing \n"; | |
if(IsEmpty()) | |
{ | |
cout<<"Error: Queue is Empty\n"; | |
return; | |
} | |
else if(front == rear ) | |
{ | |
rear = front = -1; | |
} | |
else | |
{ | |
front = (front+1)%MAX_SIZE; | |
} | |
} | |
// Returns element at front of queue. | |
int Front() | |
{ | |
if(front == -1) | |
{ | |
cout<<"Error: cannot return front from empty queue\n"; | |
return -1; | |
} | |
return A[front]; | |
} | |
/* | |
Printing the elements in queue from front to rear. | |
This function is only to test the code. | |
This is not a standard function for Queue implementation. | |
*/ | |
void Print() | |
{ | |
// Finding number of elements in queue | |
int count = (rear+MAX_SIZE-front)%MAX_SIZE + 1; | |
cout<<"Queue : "; | |
for(int i = 0; i <count; i++) | |
{ | |
int index = (front+i) % MAX_SIZE; // Index of element while travesing circularly from front | |
cout<<A[index]<<" "; | |
} | |
cout<<"\n\n"; | |
} | |
}; | |
int main() | |
{ | |
/*Driver Code to test the implementation | |
Printing the elements in Queue after each Enqueue or Dequeue | |
*/ | |
Queue Q; // creating an instance of Queue. | |
Q.Enqueue(2); Q.Print(); | |
Q.Enqueue(4); Q.Print(); | |
Q.Enqueue(6); Q.Print(); | |
Q.Dequeue(); Q.Print(); | |
Q.Enqueue(8); Q.Print(); | |
} |
Aatrox00
commented
Jun 1, 2022
via email
For a C program
#include <assert.h> // assert
#include <stdlib.h> // malloc, free
#include <stdbool.h>
#include <stdio.h>
typedef struct node
{
int data;
struct node *next;
} node_t;
typedef struct
{
node_t *rear;
int size;
} queue_t;
queue_t *alloc_queue(void)
{
queue_t *queue = malloc(sizeof(queue_t));
assert(queue != NULL);
queue->rear = NULL;
queue->size = 0;
return queue;
}
void enqueue(queue_t queue, int value)
{
assert(queue!=NULL);
node_t newnode;
node_t *front;
newnode = malloc(sizeof(node_t));
assert(newnode!=NULL);
newnode->data = value;
newnode->next = NULL;
if(queue->rear==NULL) // if the queue is empty
{
queue->rear = newnode;
queue->rear->next = queue->rear;
}
else
{
front = queue->rear->next;
queue->rear->next = newnode;
queue->rear = newnode;
queue->rear->next = front;
}
queue->size++;
}
_
int main()
{
queue_t *queue = alloc_queue();
enqueue(queue, 40);
enqueue(queue, 30);
enqueue(queue, 20);
int a;
front(queue, &a);
}