feat: add ArrayDeque (#348)
* 双向队列: java 代码 * 双向队列: markdown 内容 * Rewrite array_deque.java Update array_queue.java, linkedlist_deque.java * Add ArrayDeque figures and rewrite the contents --------- Co-authored-by: krahets <krahets@163.com>pull/371/head
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/**
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* File: array_deque.java
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* Created Time: 2023-02-16
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* Author: Krahets (krahets@163.com), FangYuan33 (374072213@qq.com)
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*/
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package chapter_stack_and_queue;
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import java.util.*;
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/* 基于环形数组实现的双向队列 */
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class ArrayDeque {
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private int[] nums; // 用于存储双向队列元素的数组
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private int front; // 队首指针,指向队首元素
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private int queSize; // 双向队列长度
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/* 构造方法 */
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public ArrayDeque(int capacity) {
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this.nums = new int[capacity];
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front = queSize = 0;
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}
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/* 获取双向队列的容量 */
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public int capacity() {
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return nums.length;
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}
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/* 获取双向队列的长度 */
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public int size() {
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return queSize;
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}
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/* 判断双向队列是否为空 */
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public boolean isEmpty() {
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return queSize == 0;
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}
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/* 计算环形数组索引 */
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private int index(int i) {
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// 通过取余操作实现数组首尾相连
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// 当 i 越过数组尾部后,回到头部
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// 当 i 越过数组头部后,回到尾部
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return (i + capacity()) % capacity();
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}
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/* 队首入队 */
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public void pushFirst(int num) {
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if (queSize == capacity()) {
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System.out.println("双向队列已满");
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return;
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}
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// 队首指针向左移动一位
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// 通过取余操作,实现 front 越过数组头部后回到尾部
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front = index(front - 1);
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// 将 num 添加至队首
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nums[front] = num;
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queSize++;
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}
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/* 队尾入队 */
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public void pushLast(int num) {
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if (queSize == capacity()) {
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System.out.println("双向队列已满");
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return;
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}
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// 计算尾指针,指向队尾索引 + 1
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int rear = index(front + queSize);
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// 将 num 添加至队尾
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nums[rear] = num;
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queSize++;
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}
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/* 队首出队 */
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public int pollFirst() {
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int num = peekFirst();
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// 队首指针向后移动一位
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front = index(front + 1);
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queSize--;
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return num;
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}
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/* 队尾出队 */
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public int pollLast() {
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int num = peekLast();
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queSize--;
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return num;
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}
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/* 访问队首元素 */
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public int peekFirst() {
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if (isEmpty())
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throw new EmptyStackException();
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return nums[front];
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}
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/* 访问队尾元素 */
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public int peekLast() {
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if (isEmpty())
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throw new EmptyStackException();
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// 计算尾元素索引
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int last = index(front + queSize - 1);
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return nums[last];
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}
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/* 返回数组用于打印 */
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public int[] toArray() {
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// 仅转换有效长度范围内的列表元素
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int[] res = new int[queSize];
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for (int i = 0, j = front; i < queSize; i++, j++) {
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res[i] = nums[index(j)];
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}
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return res;
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}
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}
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public class array_deque {
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public static void main(String[] args) {
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/* 初始化双向队列 */
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LinkedListDeque deque = new LinkedListDeque();
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deque.pushLast(3);
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deque.pushLast(2);
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deque.pushLast(5);
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System.out.println("双向队列 deque = " + Arrays.toString(deque.toArray()));
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/* 访问元素 */
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int peekFirst = deque.peekFirst();
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System.out.println("队首元素 peekFirst = " + peekFirst);
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int peekLast = deque.peekLast();
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System.out.println("队尾元素 peekLast = " + peekLast);
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/* 元素入队 */
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deque.pushLast(4);
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System.out.println("元素 4 队尾入队后 deque = " + Arrays.toString(deque.toArray()));
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deque.pushFirst(1);
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System.out.println("元素 1 队首入队后 deque = " + Arrays.toString(deque.toArray()));
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/* 元素出队 */
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int pollLast = deque.pollLast();
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System.out.println("队尾出队元素 = " + pollLast + ",队尾出队后 deque = " + Arrays.toString(deque.toArray()));
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int pollFirst = deque.pollFirst();
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System.out.println("队首出队元素 = " + pollFirst + ",队首出队后 deque = " + Arrays.toString(deque.toArray()));
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/* 获取双向队列的长度 */
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int size = deque.size();
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System.out.println("双向队列长度 size = " + size);
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/* 判断双向队列是否为空 */
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boolean isEmpty = deque.isEmpty();
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System.out.println("双向队列是否为空 = " + isEmpty);
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}
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}
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