C program for insertion and deletion in simple queue?

Answer 1

# include<iostream.h>
# include<conio.h>
# define SIZE 20

class queue
{
int a[SIZE];
int front;
int rear;
public:
queue();
~queue();
void insert(int i);
int remove();
int isempty();
int isfull();
};

queue::queue()
{
front=0;
rear=0;
}
queue::~queue()
{
delete []a;
}
void queue::insert(int i)
{
if(isfull())
{
cout<<"******Queue is FULL !!!No insertion allowed further.******";
return;
}
a[rear] = i;
rear++;
}
int queue::remove()
{
if(isempty())
{
cout<<"******Queue Empty !!!Value returned will be garbage.******";
return (-9999);
}

return(a[front++]);
}
int queue::isempty()
{
if(front == rear)
return 1;
else
return 0;
}
int queue::isfull()
{
if(rear == SIZE)
return 1;
else
return 0;
}

void main()
{
clrscr();
queue q;
q.insert(1);
q.insert(2);
cout<<""<<q.remove();
cout<<""<<q.remove();
cout<<""<<q.remove();
getch();
}

Answer 2

// Justin C. Miller
// made on : 11-27-2001
// made for: http://www.geocities.com/neonprimetime.geo/index.html

// Simple QUEUE in c++
// FIFO (first-in-first-out)

#include <iostream>
//#include <cassert>
using namespace std ;

const int max_capacity = 20 ; // if client specifies no max_capacity
const int EMPTY = -6969 ; // constant defining empty, hopefully
  // client doesn't use this number in data

// the queue class begins here
class queue{
private:
int q_front ;  // index of front of the queue
int max_capacity ; // max_capacity for the queue
int q_length ;  // length (or number of elements in queue)
int * q ;      // the array the queue is stored in
bool empty(void)const{return (this->q_length == 0) ;}
bool full(void)const{return (this->q_length == this->max_capacity);}
public:
queue(void){  // constructor when no max_capacity is specified
this->q_front = 0 ;
this->q_length = 0 ;
this->max_capacity = max_capacity ; // use global max_capacity
q = new int[this->max_capacity] ;
clear() ;  // set every element to EMPTY constant
}
queue(int max_capacity){  // constructor with max_capacity
if(this->max_capacity <= 0) this->max_capacity = max_capacity ;
this->q_front = 0 ;
this->q_length = 0;
this->max_capacity = max_capacity ; // use client's max_capacity
q = new int[this->max_capacity] ;
clear() ;  // set every element to EMPTY constant
}
~queue(void){delete this->q ;}
int length(void)const{return (this->q_length) ; } // get queue's length
bool enqueue(int x){ // append element to back of queue
if(empty()) this->q_front = 0 ;
if(full()) return false ;
int end = this->q_front + this->q_length ;
if(end >= this->max_capacity)
end = end % this->max_capacity ;
this->q[end] = x ;
this->q_length++ ;
return true ;
}
int dequeue(void){ // retrieve first element from queue, remove it
if(empty()) return EMPTY ;
int temp = this->q[this->q_front] ;
this->q[this->q_front] = EMPTY ;
this->q_front++ ;
if(this->q_front >= this->max_capacity)
this->q_front = this->q_front % this->max_capacity ;
this->q_length-- ;
return temp ;
}
void clear(void){  // clear queue
this->q_length = 0 ;
for(int i = 0 ; i < this->max_capacity ; i++)
this->q[i] = EMPTY ;
}
void print(void){ // print queue's contents
cout << "Top of List is Top Priority" << endl ;
cout << "---------------------------" << endl ;
cout << "Front:" << this->q_front << endl ;
cout << "Length:" << this->q_length << endl ;
cout << "Max Capacity:" << this->max_capacity << endl ;
if(empty()) {cout << "Empty Queue!" << endl ; return ;}
int counter = 1 ;
int end = this->q_front + this->q_length ;
if(end >= this->max_capacity)
end = end % this->max_capacity ;
for(int i = this->q_front ; counter <= this->q_length; i++, counter++){
if(i >= max_capacity)
i = 0 ;
cout << "Data " << counter << ".) " << this->q[i] << endl ;
}
}
}; // end of queue class


// main, driver program
int main(){
int num ;  // used for keyboard input
cout << "What size queue?" << endl ;
cin >> num ;
queue q(num) ; // create queue named q of size num
char input ;
while(true){
// main menu
cout << "What would you like to do?" << endl ;
cout << "(E)nqueue" << endl ;
cout << "(D)equeue" << endl ;
cout << "(C)lear all" << endl ;
cout << "(L)ength of Queue" << endl ;
cout << "(P)rint Queue" << endl ;
cout << "(Q)uit" << endl ;
cin >> input ;
switch(input){
case 'E':
case 'e':
cout << "Enter number to enqueue:" << endl ;
cin >> num ;
if(q.enqueue(num))
cout << "Enqueue successful!" << endl ;
else
cout << "Queue is full, failure!" << endl ;
break ;
case 'D':
case 'd':
num = q.dequeue() ;
if(num == EMPTY)
cout << "Queue was empty!" << endl ;
else
cout << "Number dequeued was " << num << endl ;
break ;
case 'C':
case 'c':
q.clear() ;
break ;
case 'L':
case 'l':
cout << "Length is " << q.length() << endl ;
break ;
case 'P':
case 'p':
q.print() ;
break ;
case 'Q':
case 'q':
return 0 ;
}
}
}