Write a program to implement priority queue in C?

Answer 1

A priority queue is a type of data structure that allows for elements to be inserted in any order, and to be retrieved in the order of some priority, defined by the creator. It can be implemented in any programming language, including C. For more details, see related links.

Answer 2

#include

#include

enum{FALSE=0,TRUE=-1};

/////////////////////////////////

///// Implements Priority Queue

/////////////////////////////////

class PriorityQueue // Class Prioriry Queue

{

private:

struct Node // Node of Priority Queue

{

struct Node *Previous;

int Data;

struct Node *Next;

}Current;

struct Node *head; // Pointer to Head

struct Node *ptr;

// Pointer for travelling through Queue

static int NumOfNodes;

// Keeps track of Number of nodes

public:

PriorityQueue(void);

int Maximum(void);

int Minimum(void);

void Insert(int);

int Delete(int);

void Display(void);

int Search (int);

~PriorityQueue(void);

};

// First Nodes Created With Constructor

int PriorityQueue::NumOfNodes=1;

// Constructor

PriorityQueue::PriorityQueue(void)

{

Current.Previous=NULL;

cout<<"Enter First Element of Queue"<

cin>>Current.Data;

Current.Next=NULL;

head=&Current;

ptr=head;

}

// Function Finding Maximum Priority Element

int PriorityQueue::Maximum(void)

{

int Temp;

ptr=head;

Temp=ptr->Data;

while(ptr->Next!=NULL)

{

if(ptr->Data>Temp)

Temp=ptr->Data;

ptr=ptr->Next;

}

if(ptr->Next==NULL && ptr->Data>Temp)

Temp=ptr->Data;

return(Temp);

}

// Function Finding Minimum Priority Element

int PriorityQueue::Minimum(void)

{

int Temp;

ptr=head;

Temp=ptr->Data;

while(ptr->Next!=NULL)

{

if(ptr->Data

Temp=ptr->Data;

ptr=ptr->Next;

}

if(ptr->Next==NULL && ptr->Data

Temp=ptr->Data;

return(Temp);

}

// Function inserting element in Priority Queue

void PriorityQueue::Insert(int DT)

{

struct Node *newnode;

newnode=new Node;

newnode->Data=DT;

while(ptr->Next!=NULL)

ptr=ptr->Next;

if(ptr->Next==NULL)

{

newnode->Next=ptr->Next;

ptr->Next=newnode;

}

NumOfNodes++;

}

// Function deleting element in Priority Queue

int PriorityQueue::Delete(int DataDel)

{

struct Node *mynode,*temp;

ptr=head;

if(NumOfNodes==1)

{

cout<<"Cannot Delete the only Node"<

return FALSE;

}

if(ptr->Data==DataDel)

{

/*** Checking condition for deletion of first node ***/

temp=ptr;

ptr=ptr->Next;

ptr->Previous=NULL;

//delete temp;

head=ptr;

NumOfNodes--;

return(TRUE);

}

else

{

while(ptr->Next->Next!=NULL)

{

/*** Checking condition for deletion of ***/

/*** all nodes except first and last node ***/

if(ptr->Next->Data==DataDel)

{

mynode=ptr;

temp=ptr->Next;

mynode->Next=mynode->Next->Next;

mynode->Next->Previous=ptr;

delete temp;

NumOfNodes--;

return(TRUE);

}

ptr=ptr->Next;

}

if(ptr->Next->Next==NULL && ptr->Next->Data==DataDel)

{

/*** Checking condition for deletion of last node ***/

temp=ptr->Next;

delete temp;

ptr->Next=NULL;

NumOfNodes--;

return(TRUE);

}

}

return(FALSE);

}

// Function Searching element in Priority Queue

int PriorityQueue::Search(int DataSearch)

{

ptr=head;

while(ptr->Next!=NULL)

{

if(ptr->Data==DataSearch)

return ptr->Data;

ptr=ptr->Next;

}

if(ptr->Next==NULL && ptr->Data==DataSearch)

return ptr->Data;

return(FALSE);

}

// Function Displaying elements of Priority Queue

void PriorityQueue::Display(void)

{

ptr=head;

cout<<"Priority Queue is as Follows:-"<

while(ptr!=NULL)

{

cout<Data<

ptr=ptr->Next;

}

}

// Destructor of Priority Queue

PriorityQueue::~PriorityQueue(void)

{

struct Node *temp; /* Temporary variable */

while(head->Next!=NULL)

{

temp=head->Next;

// delete head;

head=temp;

}

if(head->Next==NULL)

delete head;

}

//Main Function

void main()

{

PriorityQueue PQ;

int choice;

int DT;

while(1)

{

cout<<"Enter your choice"<

cout<<"1. Insert an element"<

cout<<"2. Display a priorty Queue"<

cout<<"3. Delete an element"<

cout<<"4. Search an element"<

cout<<"5. Exit"<

cin>>choice;

switch(choice)

{

case 1:

cout<<"Enter a Data to enter Queue"<

cin>>DT;

PQ.Insert(DT);

break;

case 2:

PQ.Display();

break;

case 3:

{

int choice;

cout<<"Enter your choice"<

cout<<"1. Maximum Priority Queue"<

cout<<"2. Minimum Priority Queue"<

cin>>choice;

switch(choice)

{

case 1:

PQ.Delete(PQ.Maximum());

break;

case 2:

PQ.Delete(PQ.Minimum());

break;

default:

cout<<"Sorry Not a correct choice"<

}

}

break;

case 4:

cout<<"Enter a Data to Search in Queue"<

cin>>DT;

if(PQ.Search(DT)!=FALSE)

cout<

else

cout<

break;

case 5:

exit(0);

default:

cout<<"Cannot process your choice"<

}

}

}

Answer 3

A priority queue is a queue in which each element is inserted or deleted on the basis of their priority. A higher priority element is added first before any lower priority element. If in case priority of two element is same then they are added to the queue on FCFS basis (first come first serve). Mainly there are two kinds of priority queue: 1) Static priority queue 2) Dynamic priority queue

Answer 4

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