本文根据《大话数据结构》一书,实现了Java版的双向链表。
在每个数据结点中都有两个指针,分别指向直接后继和直接前驱,这样的链表称为双向链表。
双向链表的结构如图所示:
- 查找元素可以根据元素的位置,分别沿正向和反向查找。
双向链表实现程序:
package DuLinkList;public class DuLinkList{ private Node head; private int count; /** * 结点 */ class Node { E data; Node prior; Node next; public Node(E data, Node prior, Node next) { this.data = data; this.prior = prior; this.next = next; } } /** * 线性表的初始化 */ public DuLinkList() { head = new Node (null, null, null); head.prior = head.next = head; count = 0; } /** * 获取第i个元素 */ public Node getElement(int i) { if (count == 0) throw new RuntimeException("空表,无法查找!"); if (i < 1 || i > count) throw new RuntimeException("查找位置错误!"); Node node = head.next; for (int j = 1; j < i; j++) { node = node.next; } return node; } /** * 在第i个位置插入元素 */ public void listInsert(int i, E data) { if (i < 1 || i > count + 1) throw new RuntimeException("插入位置错误!"); Node node = new Node (data, null, null); if (i == 1) { node.next = head.next; node.prior = head; head.next.prior = node; head.next = node; } else { Node pNode = getElement(i - 1); node.next = pNode.next; node.prior = pNode; pNode.next.prior = node; pNode.next = node; } count++; } /** * 删除第i个元素 */ public E listDelete(int i) { if (i < 1 || i > count) throw new RuntimeException("删除位置错误!"); Node node = getElement(i); E e = node.data; if (i == 1) { head.next = node.next; node.next.prior = node.prior; node = null; } else { node.next.prior = node.prior; node.prior.next = node.next; node = null; } count--; return e; } public int listLength() { return count; }}
测试程序:
package DuLinkList;public class DuLinkListTest { public static void main(String[] args) { DuLinkListstudents = new DuLinkList (); System.out.println("——————————插入1到5,并读取内容——————————"); Student[] stus = { new Student("小A", 11), new Student("小B", 12), new Student("小C", 13), new Student("小D", 14), new Student("小E", 151) }; for (int i = 1; i <= 5; i++) students.listInsert(i, stus[i - 1]); System.out.println("表长:" + students.listLength()); Student stu; for (int i = 1; i <= 5; i++) { stu = students.getElement(i).data; System.out.println("第" + i + "个位置为:" + stu.name); } System.out.println("——————————删除小A、小E——————————"); stu = students.listDelete(1); System.out.println("已删除:" + stu.name); stu = students.listDelete(4); System.out.println("已删除:" + stu.name); System.out.println("当前表长:" + students.listLength()); for (int i = 1; i <= students.listLength(); i++) { stu = students.getElement(i).data; System.out.println("第" + i + "个位置为:" + stu.name); } }}class Student { public Student(String name, int age) { this.name = name; this.age = age; } String name; int age;}
——————————插入1到5,并读取内容——————————表长:5第1个位置为:小A第2个位置为:小B第3个位置为:小C第4个位置为:小D第5个位置为:小E——————————删除小A、小E——————————已删除:小A已删除:小E当前表长:3第1个位置为:小B第2个位置为:小C第3个位置为:小D
——————————————————————————
在阅读过他人的博客后,发现自己的查找方法没有利用好双链表的特性,重写查找方法如下:
/** * 获取第i个元素 */ public NodegetElement(int i) { if (count == 0) throw new RuntimeException("空表,无法查找!"); if (i < 1 || i > count) throw new RuntimeException("查找位置错误!"); if (i <= count / 2) { // 正向查找 Node node = head.next; for (int j = 1; j < i; j++) { node = node.next; } return node; } else { // 反向查找 Node node = head.prior; int k = count - i; for (int j = 0; j < k; j++) { node = node.prior; } return node; } }
本文中只编写了查找和删除部分的程序,完整的双向链表程序可参阅这篇博客: