snippets/Queue.cpp at main · runtime-algorithms/snippets · GitHub

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#include <iostream>

#include "NodeTypes.h"
#include "Queue.h"

using namespace std;


Queue * initQueue () {
	Queue * q = new Queue;
	q->top = NULL;
	q->last = NULL;
	return q;
}


bool isEmptyQueue (Queue * q) {
	if (q->top == NULL)
		return true;
	else
		return false;
}


int sizeQueue (Queue * q) {

	LLNode * curr;
	int size;

	curr = q->top;
	size = 0;

	while (curr != NULL) {
		curr = curr->next;
		size = size + 1;
	}

	return size;
}

void enqueue (Queue * q, BTNode * data) {
	LLNode * newElement = new LLNode;
	newElement->data = data;
	newElement->next = NULL;

	if (isEmptyQueue(q)) {
		q->top = newElement;
		q->last = newElement;
	}
	else {
		q->last->next = newElement;
		q->last = newElement;
	}
}


BTNode * dequeue (Queue * q) {
	if (isEmptyQueue(q))
		return NULL; 				// to indicate error if dequeuing from an empty queue

	LLNode * toRemove;
	BTNode * data;

	toRemove = q->top;
	data = toRemove->data;
	q->top = toRemove->next;
	if (q->top == NULL)
		q->last = NULL;

	delete (toRemove);

	return data;
}