- 双链表的代码实现
import java.util.NoSuchElementException;public class MyLinkedList<E> {// 虚拟头尾节点final private Node<E> head, tail;private int size;// 双链表节点private static class Node<E> {E val;Node<E> next;Node<E> prev;Node(E val) {this.val = val;}}// 构造函数初始化虚拟头尾节点public MyLinkedList() {this.head = new Node<>(null);this.tail = new Node<>(null);head.next = tail;tail.prev = head;this.size = 0;}// ***** 增 *****public void addLast(E e) {Node<E> x = new Node<>(e);Node<E> temp = tail.prev;// temp <-> xtemp.next = x;x.prev = temp;x.next = tail;tail.prev = x;// temp <-> x <-> tailsize++;}public void addFirst(E e) {Node<E> x = new Node<>(e);Node<E> temp = head.next;// head <-> temptemp.prev = x;x.next = temp;head.next = x;x.prev = head;// head <-> x <-> tempsize++;}public void add(int index, E element) {checkPositionIndex(index);if (index == size) {addLast(element);return;}// 找到 index 对应的 NodeNode<E> p = getNode(index);Node<E> temp = p.prev;// temp <-> p// 新要插入的 NodeNode<E> x = new Node<>(element);p.prev = x;temp.next = x;x.prev = temp;x.next = p;// temp <-> x <-> psize++;}// ***** 删 *****public E removeFirst() {if (size < 1) {throw new NoSuchElementException();}// 虚拟节点的存在是我们不用考虑空指针的问题Node<E> x = head.next;Node<E> temp = x.next;// head <-> x <-> temphead.next = temp;temp.prev = head;x.prev = null;x.next = null;// head <-> tempsize--;return x.val;}public E removeLast() {if (size < 1) {throw new NoSuchElementException();}Node<E> x = tail.prev;Node<E> temp = tail.prev.prev;// temp <-> x <-> tailtail.prev = temp;temp.next = tail;x.prev = null;x.next = null;// temp <-> tailsize--;return x.val;}public E remove(int index) {checkElementIndex(index);// 找到 index 对应的 NodeNode<E> x = getNode(index);Node<E> prev = x.prev;Node<E> next = x.next;// prev <-> x <-> nextprev.next = next;next.prev = prev;x.prev = x.next = null;// prev <-> nextsize--;return x.val;}// ***** 查 *****public E get(int index) {checkElementIndex(index);// 找到 index 对应的 NodeNode<E> p = getNode(index);return p.val;}public E getFirst() {if (size < 1) {throw new NoSuchElementException();}return head.next.val;}public E getLast() {if (size < 1) {throw new NoSuchElementException();}return tail.prev.val;}// ***** 改 *****public E set(int index, E val) {checkElementIndex(index);// 找到 index 对应的 NodeNode<E> p = getNode(index);E oldVal = p.val;p.val = val;return oldVal;}// ***** 其他工具函数 *****public int size() {return size;}public boolean isEmpty() {return size == 0;}private Node<E> getNode(int index) {checkElementIndex(index);Node<E> p = head.next;// TODO: 可以优化，通过 index 判断从 head 还是 tail 开始遍历for (int i = 0; i < index; i++) {p = p.next;}return p;}private boolean isElementIndex(int index) {return index >= 0 && index < size;}private boolean isPositionIndex(int index) {return index >= 0 && index <= size;}// 检查 index 索引位置是否可以存在元素private void checkElementIndex(int index) {if (!isElementIndex(index))throw new IndexOutOfBoundsException("Index: " + index + ", Size: " + size);}// 检查 index 索引位置是否可以添加元素private void checkPositionIndex(int index) {if (!isPositionIndex(index))throw new IndexOutOfBoundsException("Index: " + index + ", Size: " + size);}private void display() {System.out.println("size = " + size);for (Node<E> p = head.next; p != tail; p = p.next) {System.out.print(p.val + " <-> ");}System.out.println("null");System.out.println();}public static void main(String[] args) {MyLinkedList<Integer> list = new MyLinkedList<>();list.addLast(1);list.addLast(2);list.addLast(3);list.addFirst(0);list.add(2, 100);list.display();// size = 5// 0 <-> 1 <-> 100 <-> 2 -> 3 -> null}
}
- 单链表的代码实现
import java.util.NoSuchElementException;public class MyLinkedList2<E> {private static class Node<E> {E val;Node<E> next;Node(E val) {this.val = val;this.next = null;}}private Node<E> head;// 实际的尾部节点引用private Node<E> tail;private int size;public MyLinkedList2() {this.head = new Node<>(null);this.tail = head;this.size = 0;}public void addFirst(E e) {Node<E> newNode = new Node<>(e);newNode.next = head.next;head.next = newNode;if (size == 0) {tail = newNode;}size++;}public void addLast(E e) {Node<E> newNode = new Node<>(e);tail.next = newNode;tail = newNode;size++;}public void add(int index, E element) {checkPositionIndex(index);if (index == size) {addLast(element);return;}Node<E> prev = head;for (int i = 0; i < index; i++) {prev = prev.next;}Node<E> newNode = new Node<>(element);newNode.next = prev.next;prev.next = newNode;size++;}public E removeFirst() {if (isEmpty()) {throw new NoSuchElementException();}Node<E> first = head.next;head.next = first.next;if (size == 1) {tail = head;}size--;return first.val;}public E removeLast() {if (isEmpty()) {throw new NoSuchElementException();}Node<E> prev = head;while (prev.next != tail) {prev = prev.next;}E val = tail.val;prev.next = null;tail = prev;size--;return val;}public E remove(int index) {checkElementIndex(index);Node<E> prev = head;for (int i = 0; i < index; i++) {prev = prev.next;}Node<E> nodeToRemove = prev.next;prev.next = nodeToRemove.next;// 删除的是最后一个元素if (index == size - 1) {tail = prev;}size--;return nodeToRemove.val;}// ***** 查 *****public E getFirst() {if (isEmpty()) {throw new NoSuchElementException();}return head.next.val;}public E getLast() {if (isEmpty()) {throw new NoSuchElementException();}return getNode(size - 1).val;}public E get(int index) {checkElementIndex(index);Node<E> p = getNode(index);return p.val;}// ***** 改 *****public E set(int index, E element) {checkElementIndex(index);Node<E> p = getNode(index);E oldVal = p.val;p.val = element;return oldVal;}// ***** 其他工具函数 *****public int size() {return size;}public boolean isEmpty() {return size == 0;}private boolean isElementIndex(int index) {return index >= 0 && index < size;}private boolean isPositionIndex(int index) {return index >= 0 && index <= size;}// 检查 index 索引位置是否可以存在元素private void checkElementIndex(int index) {if (!isElementIndex(index))throw new IndexOutOfBoundsException("Index: " + index + ", Size: " + size);}// 检查 index 索引位置是否可以添加元素private void checkPositionIndex(int index) {if (!isPositionIndex(index))throw new IndexOutOfBoundsException("Index: " + index + ", Size: " + size);}// 返回 index 对应的 Node// 注意：请保证传入的 index 是合法的private Node<E> getNode(int index) {Node<E> p = head.next;for (int i = 0; i < index; i++) {p = p.next;}return p;}public static void main(String[] args) {MyLinkedList2<Integer> list = new MyLinkedList2<>();list.addFirst(1);list.addFirst(2);list.addLast(3);list.addLast(4);list.add(2, 5);System.out.println(list.removeFirst()); // 2System.out.println(list.removeLast()); // 4System.out.println(list.remove(1)); // 5System.out.println(list.getFirst()); // 1System.out.println(list.getLast()); // 3System.out.println(list.get(1)); // 3}
}
