05-单向循环链表

//其他跟单向列表一样，add操作需要注意的地方
public void add(int index, E element) {
        // TODO Auto-generated method stub
        rangeCheekForAdd(index);
        if (index == 0) {
            Node<E> newFirst = new Node<>(element, first);
            //拿到最后一个节点
            Node<E> last = (size == 0)? newFirst:node(size-1);
            last.next = newFirst;
            first = newFirst;
        }else {
            Node<E>  prev = node(index - 1);
            prev.next = new Node<> (element, prev.next);
        }
        size ++;
}

---

public E remove(int index) {
        // TODO Auto-generated method stub
        Node<E> node = first;
        if (index == 0) {
            if (size == 1) {
                first = null;
            }else {
                Node<E> last = node(size-1);
                first = first.next;
                last.next = first;
            }
        }else {
            Node<E> prev = node(index - 1);
            node = prev.next;
            prev.next = node.next;
        }
        size --;
        return node.element;
    }

---

代码如下：

package com.weyan;

public class SingleCircleLinkedList<E> implements List<E> {
    private static final int ELEMENT_NOT_FOUND = -1;
    private int size;
    private Node<E> first;
    
    //内部类
    private static class Node<E> {
        E element;
        Node<E> next;
        //构造函数
        public Node(E element, Node<E> next) {
            super();
            this.element = element;
            this.next = next;
        }
        
    }

    @Override
    public void clear() {
        // TODO Auto-generated method stub
        size = 0;
        first = null;
    }

    @Override
    public int size() {
        // TODO Auto-generated method stub
        return size;
    }

    @Override
    public boolean isEmpty() {
        // TODO Auto-generated method stub
        return size == 0;
    }

    @Override
    public boolean contains(E element) {
        // TODO Auto-generated method stub
        return indexOf(element) != ELEMENT_NOT_FOUND;
    }

    @Override
    public void add(E element) {
        // TODO Auto-generated method stub
        add(size, element);
    }

    @Override
    public E get(int index) {
        // TODO Auto-generated method stub
        return node(index).element;
    }

    @Override
    public E set(int index, E element) {
        // TODO Auto-generated method stub
        Node<E> node = node(index);
        E old = node.element;
        node.element = element;
        return old;
    }

    @Override
    public void add(int index, E element) {
        // TODO Auto-generated method stub
        rangeCheekForAdd(index);
        if (index == 0) {
            Node<E> newFirst = new Node<>(element, first);
            //拿到最后一个节点
            Node<E> last = (size == 0)? newFirst:node(size-1);
            last.next = newFirst;
            first = newFirst;
        }else {
            Node<E>  prev = node(index - 1);
            prev.next = new Node<> (element, prev.next);
        }
        size ++;
    }

    @Override
    public E remove(int index) {
        // TODO Auto-generated method stub
        Node<E> node = first;
        if (index == 0) {
            if (size == 1) {
                first = null;
            }else {
                Node<E> last = node(size-1);
                first = first.next;
                last.next = first;
            }
        }else {
            Node<E> prev = node(index - 1);
            node = prev.next;
            prev.next = node.next;
        }
        size --;
        return node.element;
    }

    @Override
    public int indexOf(E element) {
        // TODO Auto-generated method stub
        Node<E> node = first;
        if (element == null) {
            for (int i = 0; i < size; i++) {
                if (node.element == null) return i;
                node = node.next;
            }
        }else {
            for (int i = 0; i < size; i++) {
                if (element.equals(node.element)) return i;
                node = node.next;
            }
        }
        return ELEMENT_NOT_FOUND;
    }
    
    /**
     * 获取index位置对应的节点对象
     */
    private Node<E> node(int index) {
        rangeCheck(index);
        Node<E> node = first;
        for (int i = 0; i < index; i++) {
            node = node.next;
        }
        return node;
    }
    
    private void outOfBounds(int index) {
        throw new IndexOutOfBoundsException("Index:" + index + ",size:" + size);
    }
    
    private void rangeCheck(int index) {
        // TODO Auto-generated method stub
        if (index < 0 || index >= size) {
            outOfBounds(index);
        }
    }
    
    public void rangeCheekForAdd(int index) {
        // TODO Auto-generated constructor stub
        if (index < 0 || index > size) {
            outOfBounds(index);
        }
    }
    
    @Override
    public String toString() {
        // TODO Auto-generated method stub
        StringBuilder stringBuilder = new StringBuilder();
        stringBuilder.append("size=").append(size).append(",[");
        Node<E> node = first;
        for (int i = 0; i < size; i++) {
            if (i != 0) {
                stringBuilder.append(", ");
            }
            stringBuilder.append(node.element);
            node = node.next;
        }
        stringBuilder.append("]");
        return stringBuilder.toString();
    }
    
}

验证结果：