From 36d6b5133f288c60dbe0622ddbad08dde9efdf0b Mon Sep 17 00:00:00 2001 From: Libin Yang Date: Sun, 17 Feb 2019 09:18:50 +0800 Subject: [PATCH] Update PriorityQueues.java --- DataStructures/Queues/PriorityQueues.java | 205 +++++++++++----------- 1 file changed, 103 insertions(+), 102 deletions(-) diff --git a/DataStructures/Queues/PriorityQueues.java b/DataStructures/Queues/PriorityQueues.java index 3eb74ecf..e709b136 100644 --- a/DataStructures/Queues/PriorityQueues.java +++ b/DataStructures/Queues/PriorityQueues.java @@ -1,127 +1,128 @@ /** * This class implements a PriorityQueue. - * + *

* A priority queue adds elements into positions based on their priority. * So the most important elements are placed at the front/on the top. * In this example I give numbers that are bigger, a higher priority. * Queues in theory have no fixed size but when using an array * implementation it does. - * - * @author Unknown * */ -class PriorityQueue{ - /** The max size of the queue */ - private int maxSize; - /** The array for the queue */ - private int[] queueArray; - /** How many items are in the queue */ - private int nItems; +class PriorityQueue { + /** + * The max size of the queue + */ + private int maxSize; + /** + * The array for the queue + */ + private int[] queueArray; + /** + * How many items are in the queue + */ + private int nItems; - /** - * Constructor - * - * @param size Size of the queue - */ - public PriorityQueue(int size){ - maxSize = size; - queueArray = new int[size]; - nItems = 0; - } + /** + * Constructor + * + * @param size Size of the queue + */ + public PriorityQueue(int size) { + maxSize = size; + queueArray = new int[size]; + nItems = 0; + } - /** - * Inserts an element in it's appropriate place - * - * @param value Value to be inserted - */ - public void insert(int value){ - if(nItems == 0){ - queueArray[0] = value; - nItems++; - } - else if(isFull()){ //does not insert value when the queue is full - System.out.println("Queue is full"); - } - else{ - int j = nItems; - while(j > 0 && queueArray[j-1] > value){ - queueArray[j] = queueArray[j-1]; //Shifts every element up to make room for insertion - j--; - } - queueArray[j] = value; //Once the correct position is found the value is inserted - nItems++; - } - } + /** + * Inserts an element in it's appropriate place + * + * @param value Value to be inserted + */ + public void insert(int value) { + if (isFull()) { + throw new RuntimeException("Queue is full"); + } + if (nItems == 0) { + queueArray[0] = value; + } else { + int j = nItems; + while (j > 0 && queueArray[j - 1] > value) { + queueArray[j] = queueArray[j - 1]; // Shifts every element up to make room for insertion + j--; + } + queueArray[j] = value; // Once the correct position is found the value is inserted + } + nItems++; + } - /** - * Remove the element from the front of the queue - * - * @return The element removed - */ - public int remove(){ - return queueArray[--nItems]; - } + /** + * Remove the element from the front of the queue + * + * @return The element removed + */ + public int remove() { + return queueArray[--nItems]; + } - /** - * Checks what's at the front of the queue - * - * @return element at the front of the queue - */ - public int peek(){ - return queueArray[nItems-1]; - } + /** + * Checks what's at the front of the queue + * + * @return element at the front of the queue + */ + public int peek() { + return queueArray[nItems - 1]; + } - /** - * Returns true if the queue is empty - * - * @return true if the queue is empty - */ - public boolean isEmpty(){ - return(nItems == 0); - } + /** + * Returns true if the queue is empty + * + * @return true if the queue is empty + */ + public boolean isEmpty() { + return (nItems == 0); + } - /** - * Returns true if the queue is full - * - * @return true if the queue is full - */ - public boolean isFull(){ - return(nItems == maxSize); - } + /** + * Returns true if the queue is full + * + * @return true if the queue is full + */ + public boolean isFull() { + return (nItems == maxSize); + } - /** - * Returns the number of elements in the queue - * - * @return number of elements in the queue - */ - public int getSize(){ - return nItems; - } + /** + * Returns the number of elements in the queue + * + * @return number of elements in the queue + */ + public int getSize() { + return nItems; + } } /** * This class implements the PriorityQueue class above. - * - * @author Unknown * + * @author Unknown */ -public class PriorityQueues{ - /** - * Main method - * - * @param args Command Line Arguments - */ - public static void main(String args[]){ - PriorityQueue myQueue = new PriorityQueue(4); - myQueue.insert(10); - myQueue.insert(2); - myQueue.insert(5); - myQueue.insert(3); - //[2, 3, 5, 10] Here higher numbers have higher priority, so they are on the top +public class PriorityQueues { + /** + * Main method + * + * @param args Command Line Arguments + */ + public static void main(String[] args) { + PriorityQueue myQueue = new PriorityQueue(4); + myQueue.insert(10); + myQueue.insert(2); + myQueue.insert(5); + myQueue.insert(3); + // [2, 3, 5, 10] Here higher numbers have higher priority, so they are on the top - for(int i = 3; i>=0; i--) - System.out.print(myQueue.remove() + " "); //will print the queue in reverse order [10, 5, 3, 2] + for (int i = 3; i >= 0; i--) + System.out.print(myQueue.remove() + " "); // will print the queue in reverse order [10, 5, 3, 2] - //As you can see, a Priority Queue can be used as a sorting algotithm - } + // As you can see, a Priority Queue can be used as a sorting algotithm + } }