java-common-algorithms/src/main/java/dataStructures/queue/Queue.java at master · meugenom/java-common-algorithms · GitHub

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packagedataStructures.queue;

publicclassQueue {

privateint[] queue;

// constructor
publicQueue(intsize) {
queue = newint[size];
	}

/*
 * is Queue empty
 *
 * @complexity time O(1)
 * @complexity space O(1)
 */
publicbooleanisEmpty() {
returnqueue[0] == 0;
	}

/*
 * add item in the back of Queue
 *
 * @param item
 *
 * @complexity time O(n)
 * @complexity space O(1)
 */
publicvoidenqueue(intitem) {
if (queue[queue.length - 1] != 0) {
System.out.println("Queue is full");
 } else {
for (inti = 0; i < queue.length; i++) {
if (queue[i] == 0) {
queue[i] = item;
break;
 }
 }
 }
	}

/*
 * remove item from the front of Queue
 *
 * @complexity time O(n)
 * @complexity space O(1)
 */
publicvoiddequeue() {
if (isEmpty()) {
System.out.println("Queue is empty");
 } else {
//remove first item from queue
for (inti = 0; i < queue.length - 1; i++) {
queue[i] = queue[i + 1];
 }
 }
	}

/*
 * peek the front of Queue
 *
 * @complexity time O(1)
 * @complexity space O(1)
 */
publicintpeek() {
if (isEmpty()) {
System.out.println("Queue is empty");
return0;
 } else {
returnqueue[0];
 }
	}

/*
 * get size of Queue
 *
 * @complexity time O(n)
 * @complexity space O(1)
 */
publicintsize() {
intsize = 0;
for (inti = 0; i < queue.length; i++) {
if (queue[i] != 0) {
size++;
 }
 }
returnsize;
	}

/*
 * print Queue
 *
 * @complexity time O(n)
 * @complexity space O(1)
 */
publicvoidprint() {
for (inti = 0; i < queue.length; i++) {
System.out.print(queue[i] + " ");
 }
System.out.println();
	}

}