package com.woniuxy.linkedlist;

public class SingleLinkedList {
    
    private int size;   // 链表节点数
    private Node head;  // 头节点
    
    public SingleLinkedList() {
        this.size = 0;
        this.head = null;
    }
    
    // 内部类，链表节点
    private class Node {
        private Object data;    // 数据
        private Node next;      // 后继指针
        
        public Node(Object data) {
            this.data = data;
            this.next = null;
        }
    }
    
    // 头插法 添加元素
    public void add(Object data) {
        Node newHead = new Node(data);
        if (size == 0) {
            this.head = newHead;
        }
        else {
            newHead.next = this.head;
            this.head = newHead;
        }
        this.size++;
    }
    
    // 查找指定元素，找到了返回该节点，找不到返回null
    public Node find(Object data) {
        Node current = head;
        while (current != null) {
            if (data.equals(current.data)) {
                return current;
            }
            else {
                current = current.next;
            }
        }
        
        return null;
    }
    
    // 删除节点，成功删除返回true，否则返回false
    public boolean remvoe(Object data) {
        Node previous = null;
        Node current = head;
        while (current != null) {
            if (data.equals(current.data) ) {
                if (previous != null) {
                    previous.next = current.next;
                }
                // 删除头节点
                else {
                    head = current.next;
                }
                this.size--;
                return true;
            }
            previous = current;
            current = current.next;
        }

        return false;
    }
    
    // 改变节点内容，成功返回true，否则返回false
    public boolean set(Object data, Object newdata) {
        Node node = this.find(data);
        if (node != null) {
            node.data = newdata;
            return true;
        }
        return false;
    }
    
    // 输出链表
    public void print() {
        Node current = head;
        while (current != null) {
            System.out.print(current.data);
            current = current.next;
            if (current != null) {
                System.out.print(" --> ");
            }
        }
    }
    
    public static void main(String[] args) {
        SingleLinkedList linklist = new SingleLinkedList();
        linklist.add("A");
        linklist.add("B");
        linklist.add("C");
        linklist.add("D");
//        linklist.remvoe("D");
        System.out.println(linklist.find("A").data);
        System.out.println(linklist.size);
        linklist.set("A", "AA");
        linklist.print();
    }
}