Queue not working as intended.

[MH4]

Hi guys. I'm currently doing a queue system and trying to emulate a real life example of a clinic.
Patients press <1> to register their particulars. If it is full system will tell them that queue is full.
Doctor press <2> to see the next patient. If there is no more patients, the system will tell the doctor that queue is empty.
Press <3> to see who is currently in the queue.

I am using an array for this queue example. My array has a size of 4(for now).
I use the variables "first" and "last" as indexes telling me which is the first and last patient in the queue. (Eg. i use it like this: queueArray[first]. if first == 0 then patient in queueArray[0] is the first patient in the queue)

I believe that there is a problem in either my add function or my printAll function. (I have a hunch its the add function since I took 2 days to figure it out). Btw I am using classes.

Here is my current code:

#include <iostream>
#include <string>
#include "patient.h"
#include "queue.h"

using namespace std;

// constructor
queue::queue(int maxSize) {
	arraySize = maxSize;
	queueArray = new patient[maxSize]; // the array to contain patient objects
	first = -1; // a index to show who is first
	last = 0;   // a index to show who is last
};

bool queue::isEmpty () {
	if (first == -1 && last == 0) {
		return true;
	}

	else {
		return false;
	}
};

bool queue::isFull (){
	if (first == 0 && last == arraySize) {
		return true;
	}

	else {
		return false;
	}
};

void queue::add (string inputName, string inputId, int inputQueueNumber) {
	// if last is out of bounds
	if (isFull() == true) {
		cout << "Sorry Queue is full!" <<endl;
	}

	else if (isEmpty() == true) {
		// 1st initialize the patient's record
		newPatient.initialize(inputName, inputId, inputQueueNumber);

		first = 0;
		queueArray[first] = newPatient;
	}

	//else if (isFull() == false && last == arraySize) {
	//	// 1st initialize the patient's record
	//	newPatient.initialize(inputName, inputId, inputQueueNumber);

	//	last = 0;
	//	queueArray[last] = newPatient;
	//	last+=1;
	//}

	else if (last >= first) {
		last+=1;

		if (last < arraySize) {
			newPatient.initialize(inputName, inputId, inputQueueNumber);
			queueArray[last] = newPatient;
		}

		else {
			if (first != 0) {
				last = last%arraySize; //reset last index pointer

				newPatient.initialize(inputName, inputId, inputQueueNumber);
				queueArray[last] = newPatient;
			}

			else {
				cout << "Queue is full!" <<endl;
			}
		}
	};

};

void queue::dequeue(void) {
	//// move the first pointer index to the next element as
	//// the current element is not needed anymore
	//first+=1;

	// As long as array is empty then
	// move the first index pointer to the next patient
	if(isEmpty() == false) {
		first+=1;
	}

	//if (first == last) {
	//	// reset index pointers
	//	// indicates that array is empty
	//	first = -1;
	//	last = 0;
	//}

	else {
		cout << "Queue is empty!" <<endl;
	}
};

void queue::printNext(void) {
	if (isEmpty() == true) {
		cout << "There are currently no patients in the queue!" <<endl;
	}

	else if (first >= 0) {
			cout <<endl << queueArray[first];
	}
};

void queue::printAll(void) {
	if (isEmpty() == true) {
		cout << "There are currently no patients in the queue!" <<endl;
	}

	else if (first == last) {
	}
	
	else if (first < last) {
		/*for (int iterator = first; iterator < last; iterator++) {
			cout << queueArray[iterator] <<endl;
		}*/

		int f = first;

		while(f < last) {
			cout << queueArray[f];
			f++;
		}
	}

	else if (first > last) {
		int f = first;
		int l = last;

		while (f < arraySize) {
			cout << queueArray[first];
			f+=1;
		}

		while (l < first) {
			cout << queueArray[l];
			l+=1;
		}
	}

};

[MH4]

and this is my main.cpp

#include <iostream>
#include <string>
#include "patient.h"
#include "queue.h"

using namespace std;

void main (void) {
	const int maxSize = 4; // size of clinic
	queue *clinicQueue = new queue(maxSize); // the clinic

	string inputName, inputId, choice;
	int inputQueueNumber = 1;

	while (true) {
		cout << "Welcome to XYZ Clinic queueing system!" <<endl
			<< "Press <1> to get a queue number" <<endl
			<< "Press <2> to show next patient" <<endl
			<< "Press <3> to show all patients" <<endl
			<< "Press <4> to quit" <<endl
			<<endl;

		getline(cin, choice);

		if (choice == "1"){
			cout << "Input your name: ";
			getline(cin, inputName);
			cout << "Input your id: ";
			getline(cin, inputId);
			clinicQueue->add(inputName, inputId, inputQueueNumber);
			inputQueueNumber++;

		}

		else if (choice == "2"){
			clinicQueue->printNext();
			clinicQueue->dequeue();
		}

		else if (choice == "3") {
			clinicQueue->printAll();
		}

		else if (choice == "4") {
			break;
		}

		else{
			cout << "What?" <<endl;
		}

		system("pause");
		system("cls");
	}

};

[MH4]

One of the problems I encountered is when I pressed <1> and added a patient, then I pressed <3> it doesnt show the patient. But funnily enough when I added 4 patients (pressed <1> 4 times) and then pressed <3> the program shows all the patients.

Also I cant seem to add patients to the front of the array(Circular queue). If lets say queue is full and then I pressed <2> then first patient is now queueArray[1]. When I want to add the next patient to queueArray[0] I used last = last%arraySize to make. But there seems to be some problem..

[DSLq5Di1]

Looks overly complicated.. see my example code below,

public:
	bool isEmpty() { return num_of_elements == 0; }
	bool isFull() { return num_of_elements == arraySize; }
	
	void add(...)
	{
		if (!isFull())
		{
			int back = (front + num_of_elements++) % arraySize;			
			queueArray[back] = ...;
		}	
	}
	
        void dequeue()
        {
        	if (!isEmpty())
        	{
        		front = (front + 1) % arraySize;
        		--num_of_elements;
        	}
        }

        void printAll()
        {        	
        	for (int count = 0; count < num_of_elements; ++count)
        	{
        		int i = (front + count) % arraySize;
        		cout << queueArray[i];        	
        	}
        }
private:
	...
	int front, num_of_elements; // initialize to 0 in constructor 

Why does your queue::add(...) construct patients? a patient should be created outside the queue and passed in as an argument. I would also recommend using templates to make your code generic.

[MH4]

Thank you Sir! It works perfectly and your code is so easy to understand! And thanks for the advice on the templates. I will look into it :)