Program plan: Here we are running a simulation with a random integer from 1 to 4 to determine the minute at which the first customer arrives, the first customer’s service time, scheduling the arrival time of the next customer if the service was completed for the last customer. Program description: The program describes the simulation for a checkout line at a supermarket. Customers come in an integral interval of 1-4 minutes. Each customer is served in a random integer integral of 1-4 minutes. The rates need to be balanced. If the average arrival rate is larger than the average service rate, the queue will grow infinitely. Even with “balanced” rates, randomness can still cause a long queue. Program: #include <iostream> #include <ctime> #include<stdlib.h> //#include<conio.h> using namespace std; struct queueNode { /* self-referential structure */ int data; struct queueNode *nextPtr; }; typedef struct queueNode QueueNode, *QueueNodePtr; /* function prototypes */ void CustQueue( QueueNodePtr ); int isEmpty( QueueNodePtr ); char Out_queue( QueueNodePtr , QueueNodePtr ); void Into_queue( QueueNodePtr , QueueNodePtr , int ); int main() { int Total_time= 0; int Arrival_t= 0; // arrival time int Departure_t = 0; // departure and hence time needed to serve last customer int Cust_num = 0; QueueNodePtr startptr = NULL,endptr = NULL; startptr = ( QueueNodePtr ) malloc( sizeof( QueueNode ) ); endptr = ( QueueNodePtr ) malloc( sizeof( QueueNode ) ); srand((unsigned int)time(NULL)); while(Total_time<= 720) { if(Total_time== Arrival_t) { //customer arrives Cust_num++; Into_queue(startptr,endptr,Cust_num); //customer joins the Q Arrival_t+= rand()%4 + 1; cout<<"\n\ntime" << Total_time<< "customer" <<Cust_num<< "joins Q, next customer scheduled for " << Arrival_t<< endl; CustQueue(startptr); // getchar(); } if(Total_time== Departure_t) { if(!isEmpty(startptr)) { Out_queue(startptr,endptr); //customer gets serviced Departure_t += rand()%4 + 1; //time customer leaves service cout<<"time = " << Total_time<< " ,customer " <<Cust_num << "ON, next service session at "<<Departure_t<<"sec"<<endl ; } else { //if Q empty schedule service at a later time Departure_t += rand()%4 + 1; cout<<"time = "<<Total_time<< ",next service session at "<<Departure_t<<"sec"<<endl ; } CustQueue(startptr); // getchar(); } Total_time++; } CustQueue(startptr); return 0; } void Into_queue( QueueNodePtr startptr, QueueNodePtr endptr,int value ) { QueueNodePtr newPtr; newPtr = ( QueueNodePtr ) malloc( sizeof( QueueNode ) ); if ( newPtr != NULL ) { newPtr->data = value; newPtr->nextPtr = NULL; if ( isEmpty( startptr ) ) startptr = newPtr; else ( endptr )->nextPtr = newPtr; endptr = newPtr; } else cout<< value<<" not inserted. No memory available.\n" <<endl ; } char Out_queue( QueueNodePtr startptr, QueueNodePtr endptr ) { char value; QueueNodePtr tempPtr; value = ( startptr )->data; tempPtr = startptr; startptr = ( startptr )->nextPtr; if ( startptr == NULL ) endptr = NULL; free( tempPtr ); return value; } int isEmpty( QueueNodePtr startptr ) { if(startptr == NULL) return 0; else return 1; } void CustQueue( QueueNodePtr currentPtr ) { if ( currentPtr == NULL ) cout<<"Queue is empty" << endl; else { cout<<"The queue is:\n" <<endl ; while ( currentPtr != NULL ) { cout<< currentPtr->data<<" <-- " ; currentPtr = currentPtr->nextPtr; } cout<<"NULL\n\n" <<endl ; } } Sample Output: Based on the above output the following can be concluded: a) The maximum number of customers in the queue at any given point of time is 2 as can be seen from the below screenshot for instance: customer 271 arrives at time 664 and 272 arrives at 666. so two customers are waiting to be served before the next customer comes in. b) The longest wait any customer experiences is 4 seconds. c)If the arrival interval is changed to 1 to 3 minutes, the number of customers in the queue at any given point of time will reduce to 1 from 2, and so the wait time will increase as well.

C++ How To Program Sve & Mpl W/pe Etx A/c

1st Edition

ISBN: 9780134612386

Author: Deitel

Publisher: Pearson Education

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Chapter 19, Problem 19.14E

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Solution Summary: The author describes the program for a checkout line at the supermarket where customers come in an integral interval of 1-4 minutes.

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