數據結構之鏈表[Java]

/**
 * @ClassName: LinkedList
 * @Author: Leo
 * @Description: 鏈表
 * @Date: 4/9/2020 12:43 PM
 */
public class LinkedList<E> {
    /**
     * 維護的內部Node節點
     */
    private class Node {
        //存放數據
        public E e;
        //指向下一個節點
        public Node next;

        public Node(E e, Node next) {
            this.e = e;
            this.next = next;
        }

        public Node(E e) {
            this(e, null);
        }

        public Node() {
            this(null, null);
        }

        @Override
        public String toString() {
            return e.toString();
        }
    }

    //虛擬頭節點
    private Node dummyHead;
    //鏈表內元素數量
    private int size;

    public LinkedList() {
        dummyHead = new Node();
        size = 0;
    }

    /**
     * 獲取鏈表元素數量
     *
     * @return
     */
    public int getSize() {
        return size;
    }

    /**
     * 判斷鏈表是否爲空
     *
     * @return
     */
    public boolean isEmpty() {
        return size == 0;
    }

    /**
     * 向指定索引添加元素
     *
     * @param index
     * @param e
     */
    public void add(int index, E e) {
        if (index < 0 || index > size) {
            throw new IllegalArgumentException("Add failed. Illegal index.");
        }

        Node prev = dummyHead;
        for (int i = 0; i < index; i++) {
            prev = prev.next;
        }
        prev.next = new Node(e, prev.next);
        size++;
    }

    /**
     * 頭插法
     *
     * @param e
     */
    public void addFirst(E e) {
        add(0, e);
    }

    /**
     * 尾插法
     *
     * @param e
     */
    public void addLast(E e) {
        add(size, e);
    }

    /**
     * 獲取索引位置的元素
     *
     * @param index
     * @return
     */
    public E get(int index) {
        if (index < 0 || index >= size) {
            throw new IllegalArgumentException("Get failed. Illegal index.");
        }
        Node cur = dummyHead.next;
        for (int i = 0; i < index; i++) {
            cur = cur.next;
        }
        return cur.e;
    }

    /**
     * 獲取首部元素
     *
     * @return
     */
    public E getFirst() {
        return get(0);
    }

    /**
     * 獲取尾部元素
     *
     * @return
     */
    public E getLast() {
        return get(size - 1);
    }

    /**
     * 設置index位置的元素
     *
     * @param index
     * @param e
     */
    public void set(int index, E e) {
        if (index < 0 || index >= size) {
            throw new IllegalArgumentException("Set failed. Illegal index.");
        }

        Node cur = dummyHead.next;
        for (int i = 0; i < index; i++) {
            cur = cur.next;
        }
        cur.e = e;
    }

    /**
     * 判斷是否包含元素e
     *
     * @param e
     * @return
     */
    public boolean contains(E e) {
        Node cur = dummyHead.next;
        while (cur != null) {
            if (cur.e.equals(e)) {
                return true;
            }
            cur = cur.next;
        }
        return false;
    }

    /**
     * 刪除index位置的元素
     *
     * @param index
     * @return
     */
    public E remove(int index) {
        if (index < 0 || index >= size) {
            throw new IllegalArgumentException("Remove failed. Index is illegal.");
        }

        Node prev = dummyHead;
        for (int i = 0; i < index; i++) {
            prev = prev.next;
        }
        Node retNode = prev.next;
        prev.next = retNode.next;
        retNode.next = null;
        size--;
        return retNode.e;
    }

    /**
     * 刪除頭部元素
     */
    public void removeFirst() {
        remove(0);
    }

    /**
     * 刪除尾部元素
     */
    public void removeLast() {
        remove(size - 1);
    }

    /**
     * 刪除指定元素
     *
     * @param e
     */
    public void removeElement(E e) {
        Node prev = dummyHead;
        while (prev != null) {
            if (prev.next.e.equals(e)) {
                break;
            }
            prev = prev.next;
        }

        if (prev.next != null) {
            Node delNode = prev.next;
            prev.next = delNode.next;
            delNode.next = null;
            size--;
        }
    }

    @Override
    public String toString() {
        StringBuilder sb = new StringBuilder();
        Node cur = dummyHead.next;
        while (cur != null) {
            sb.append(cur + "->");
            cur = cur.next;
        }
        sb.append("NULL");
        return sb.toString();
    }
}