Java 程序实现队列数据结构
javacampus interviewserver side programmingprogramming
在本文中，我们将了解如何实现队列数据结构。队列是一种线性结构，其操作执行遵循特定的顺序。顺序为先进先出 (FIFO)。
下面是相同的演示 −
假设我们的输入是 −
输入队列:[150, 300, 450, 600]
期望输出将是 −
删除元素后，队列中的元素为:[300, 450, 600]
算法
步骤 1 - 开始 步骤 2 - 声明即 步骤 3 - 使用 ‘offer’ 方法向其中添加元素。 步骤 4 - 显示队列内容 步骤 5 - 使用 ‘poll’ 方法从队列中删除元素。 步骤 6 - 调用 ‘poll’ 方法后显示队列中的元素。 第 7 步 - 显示结果 第 8 步 - 停止
示例 1
在这里，我们使用内置定义的函数来执行所有堆栈操作。
import java.util.Queue;
import java.util.LinkedList;
public class Demo {
public static void main(String[] args) {
System.out.println("The required packages have been imported");
Queue<Integer> input_queue = new LinkedList<>();
input_queue.offer(150);
input_queue.offer(300);
input_queue.offer(450);
input_queue.offer(600);
System.out.println("The queue is defined as: " + input_queue);
int removedNumber = input_queue.poll();
System.out.println("After removing an element, the elements of the queue are: " +input_queue);
}
}
输出
The required packages have been imported The queue is defined as: [150, 300, 450, 600] After removing an element, the elements of the queue are: [300, 450, 600]
示例 2
在这里，我们使用用户定义的函数来执行所有堆栈操作。
public class Queue {
int SIZE = 5;
int items[] = new int[SIZE];
int front, rear;
Queue() {
front = -1;
rear = -1;
}
boolean isFull() {
if (front == 0 && rear == SIZE - 1) {
return true;
}
return false;
}
boolean isEmpty() {
if (front == -1)
return true;
else
return false;
}
void enQueue(int element) {
if (isFull()) {
System.out.println("\nThe queue is full");
}
else {
if (front == -1) {
front = 0;
}
rear++;
items[rear] = element;
System.out.println("\nThe element " + element + " is inserted");
}
}
int deQueue() {
int element;
if (isEmpty()) {
System.out.println("\nThe queue is empty");
return (-1);
}
else {
element = items[front];
if (front >= rear) {
front = -1;
rear = -1;
}
else {
front++;
}
System.out.println("\nThe element " +element + " is deleted");
return (element);
}
}
void display() {
int i;
if (isEmpty()) {
System.out.println("The queue is empty ");
}
else {
System.out.println("\nThe elements of the queue are: ");
for (i = front; i <= rear; i++)
System.out.print(items[i] + " ");
}
}
public static void main(String[] args) {
Queue input_queue = new Queue();
for(int i = 1; i < 6; i ++) {
input_queue.enQueue(i * 100);
}
System.out.println("The queue is defined as: " + input_queue);
input_queue.enQueue(6);
input_queue.display();
input_queue.deQueue();
input_queue.display();
}
}
输出
The element 100 is inserted The element 200 is inserted The element 300 is inserted The element 400 is inserted The element 500 is inserted The queue is defined as: Queue@2a139a55 The queue is full The elements of the queue are: 100 200 300 400 500 The element 100 is deleted The elements of the queue are: 200 300 400 500
