Day18 循环队列

1.循环队列在增加或者删除元素时头指针和尾指针都是当前位置+1，所以会出现假溢出的情况，要解决这个问题的话直接取模就可以；
2.这里为了区分空队列与满队列，留出了一个结点不放元素，则判空：head == tail，判满：head == (tail + 1) % TOTAL_SPACE；
  1 /**
  2  * Circle int queue.
  3  * 
  4  */
  5 public class CircleIntQueue {
  6     /**
  7      * The total space. One space can never be used.
  8      */
  9     public static final int TOTAL_SPACE = 10;
 10 
 11     /**
 12      * The data.
 13      */
 14     int[] data;
 15 
 16     /**
 17      * The index for calculating the head. The actual head
 18      * is head % TOTAL_SPACE.
 19      */
 20     int head;
 21 
 22     /**
 23      * The index for calculating the tail.
 24      */
 25     int tail;
 26 
 27     /**
 28      * The constructor
 29      */
 30     public CircleIntQueue() {
 31         data = new int[TOTAL_SPACE];
 32         head = 0;
 33         tail = 0;
 34     }// Of the first constructor
 35 
 36     /**
 37      * Enqueue.
 38      * 
 39      * @param paraValue The value of the new node.
 40      */
 41     public void enqueue(int paraValue) {
 42         if ((tail + 1) % TOTAL_SPACE == head) {
 43             System.out.println("Queue full.");
 44             return;
 45         } // Of if
 46 
 47         data[tail % TOTAL_SPACE] = paraValue;
 48         tail++;
 49     }// Of enqueue
 50 
 51     /**
 52      * Dequeue.
 53      * 
 54      * @return The value at the head.
 55      */
 56     public int dequeue() {
 57         if (head == tail) {
 58             System.out.println("No element in the queue");
 59             return -1;
 60         } // Of if
 61 
 62         int resultValue = data[head % TOTAL_SPACE];
 63 
 64         head++;
 65 
 66         return resultValue;
 67     }// Of dequeue
 68 
 69     /**
 70      * Overrides the method claimed in Object, the superclass
 71      * of any class.
 72      */
 73     public String toString() {
 74         String resultString = "";
 75 
 76         if (head == tail) {
 77             return "empty";
 78         } // Of if
 79 
 80         for (int i = head; i < tail; i++) {
 81             resultString += data[i % TOTAL_SPACE] + ", ";
 82         } // Of for i
 83 
 84         return resultString;
 85     }// Of toString
 86 
 87     /**
 88      * The entrance of the program.
 89      * 
 90      * @param args Not used now.
 91      */
 92     public static void main(String args[]) {
 93         CircleIntQueue tempQueue = new CircleIntQueue();
 94         System.out.println("Initialized, the list is: " + tempQueue.toString());
 95 
 96         for (int i = 0; i < 5; i++) {
 97             tempQueue.enqueue(i + 1);
 98         } // Of for i
 99         System.out.println("Enqueue, the queue is: " + tempQueue.toString());
100 
101         int tempValue = tempQueue.dequeue();
102         System.out.println("Dequeue " + tempValue + ", the queue is: " + tempQueue.toString());
103 
104         for (int i = 0; i < 6; i++) {
105             tempQueue.enqueue(i + 10);
106             System.out.println("Enqueue, the queue is: " + tempQueue.toString());
107         } // Of for i
108 
109         for (int i = 0; i < 3; i++) {
110             tempValue = tempQueue.dequeue();
111             System.out.println("Dequeue " + tempValue + ", the queue is: " + tempQueue.toString());
112         } // Of for i
113 
114         for (int i = 0; i < 6; i++) {
115             tempQueue.enqueue(i + 100);
116             System.out.println("Enqueue, the queue is: " + tempQueue.toString());
117         } // Of for i
118 
119     }// Of main
120 
121 }// Of CircleIntQueue

 

posted @ 2022-06-16 11:35  滑稽的炒饭  阅读(30)  评论(0)    收藏  举报