Introduction - What is priority Queue A priority queue is an abstract data type (ADT) supporting the following three operations: 1. Add an element to the queue with an associated priority 2. Remove the element from the queue that has the highest priority, and return it 3. (optionally) peek at the element with highest priority without removing it The Code Code: #include <iostream.h> #include <stdlib.h> 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"<<endl; 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) Temp=ptr->Data; ptr=ptr->Next; } if(ptr->Next==NULL && ptr->Data<Temp) 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"<<endl; 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:-"<<endl; while(ptr!=NULL) { cout<<ptr->Data<<endl; 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"<<endl; cout<<"1. Insert an element"<<endl; cout<<"2. Display a priorty Queue"<<endl; cout<<"3. Delete an element"<<endl; cout<<"4. Search an element"<<endl; cout<<"5. Exit"<<endl; cin>>choice; switch(choice) { case 1: cout<<"Enter a Data to enter Queue"<<endl; cin>>DT; PQ.Insert(DT); break; case 2: PQ.Display(); break; case 3: { int choice; cout<<"Enter your choice"<<endl; cout<<"1. Maximum Priority Queue"<<endl; cout<<"2. Minimum Priority Queue"<<endl; 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"<<endl; } } break; case 4: cout<<"Enter a Data to Search in Queue"<<endl; cin>>DT; if(PQ.Search(DT)!=FALSE) cout<<DT<<" Is present in Queue"<<endl; else cout<<DT<<" is Not present in Queue"<<endl; break; case 5: exit(0); default: cout<<"Cannot process your choice"<<endl; } } } Dont copy but you can download the file as an attachment. This is the priority Queue implementation and the Queue implementation can be refered here - Queue implementation using Linked List.

hello that is great i want to ask u shabbir if i want to insert the data in order by maximum node how can i do that in this function that i have it Code: // ------------- Insert ----------------// template <class type> void priorityqueue<type>::insert(type datain) { if(numberofnodes==0) { node<type> *current; current=new node<type>; current->previous=NULL; current->next=NULL; current->data=datain; head=current; ptr=head; } else if(numberofnodes>0) { node<type> *pnew; pnew= new node<type>; pnew->data=datain; while(ptr->next!=NULL) ptr=ptr->next; if(ptr->next==NULL) { pnew->next=ptr->next; ptr->next=pnew; } } numberofnodes++; } NOTE: i want the nodes ordered by maximum ------------------------------------------------------------------------------------------ another question your display function is good but if i want it print the all nodes from maximum to minimum node what is the modification ????? thanx

hi shabbir, Thanks for your immediate reply......the code is actually a bouncer to me....i forgot to mention in my post that i dont require the code....a simple explanation of how to execute that would be enough.......it would be helpful if you can explain the whole thing in simple language......... thanks in advance, siya

data in order by maximum that is great i want to ask u shabbir if i want to insert the data in order by maximum node how can i do that in this function that i have it.

this program is very helpful for me. But same question is for you that if i want to insert the data order by maximum to minimum node than what would be the function.

Salam to all , im new here , would i'll get answer for every questions on programming knowledge here?