链表：自定义双链表总结

来源：互联网发布：张清安知乎编辑：程序博客网时间：2024/04/29 23:46
双链表每个节点都有两个链prev和 next，所以相对于单链表在某些功能的实现上更简单一些。
Java实现

import java.util.Iterator;import java.util.NoSuchElementException;public class DoubleLinkedList<Item> implements Iterable<Item> {    private class Node {        private Item item;        private Node prev;        private Node next;    }    private Node first;    private Node last;    private int N;    public DoubleLinkedList() {        first = null;        last = null;    }    public DoubleLinkedList(Item[] a) {        for (Item i : a)            append(i);    }    public DoubleLinkedList(Iterable<Item> coll) {        for (Item i : coll)            append(i);    }    public int size() {        return N;    }    public boolean isEmpty() {        return size() == 0;    }    /**     * 返回头尾节点元素     *      * @return     */    public Item first() {        if (isEmpty())            throw new RuntimeException("链表为空");        return first.item;    }    public Item last() {        if (isEmpty())            throw new RuntimeException("链表为空");        return last.item;    }    /**     * 获取k位置的节点     */    public Node node(int k) {        Node curr = null;        int i = 1;        if (k > 0) {            curr = first;            while (i < k && curr != null) {                curr = curr.next;                i++;            }        } else if (k < 0) {            k = -k;            curr = first;            while (i < k && curr != null) {                curr = curr.prev;                i++;            }        }        return curr;    }    /**     * 头增     */    public void prepend(Item item) {        Node x = new Node();        x.item = item;        if (isEmpty()) {            first = x;            last = x;        } else {            x.next = first;            first.prev = x;            first = x;        }        N++;    }    /**     * 尾增     */    public void append(Item item) {        Node x = new Node();        x.item = item;        if (isEmpty()) {            first = x;            last = x;        } else {            x.prev = last;            last.next = x;            last = x;            N++;        }    }    /**     * 前插     */    public void insertBefore(Node node, Item item) {        if (node == first)            prepend(item);        else {            Node prev = node.prev;            Node x = new Node();            x.item = item;            x.prev = prev;            x.next = node;            prev.next = x;            node.prev = x;            N++;        }    }    /**     * 后插     */    public void insertAfter(Node node, Item item) {        if (node == last)            append(item);        else {            Node next = node.next;            Node x = new Node();            x.item = item;            x.prev = node;            x.next = next;            node.next = x;            next.prev = x;            N++;        }    }    /**     * 删除第一个元素     */    public Item removeFirst() {        if (isEmpty())            throw new RuntimeException("表为空");        Item item = first.item;        if (first.next != null)            first.next.prev = null;        first = first.next;        N--;        if (first == null)            last = null; // 避免游离        return item;    }    /**     * 删除最后一个元素     */    public Item removeLast() {        if (isEmpty())            throw new RuntimeException("表为空");        Item item = last.item;        if (last.prev != null)            last.prev.next = null;        last = last.prev;        N--;        if (last == null)            first = null;        return item;    }    /**     * 删除某个节点     */    public Item remove(Node node) {        if (node == first)            return removeFirst();        else if (node == last)            return removeLast();        else {            Node prev = node.prev;            Node next = node.next;            prev.next = node.next;            next.prev = node.prev;            N--;            return node.item;        }    }    /**     * 迭代器     */    @Override    public Iterator<Item> iterator() {        return new ListIterator();    }    private class ListIterator implements Iterator<Item>{        private Node current = first;        @Override        public boolean hasNext() {            return current != null;        }        @Override        public Item next() {            if(!hasNext())                throw new NoSuchElementException();            Item item = current.item;            current = current.next;            return item;        }        @Override        public void remove() {            throw new UnsupportedOperationException();        }       }}
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