题解 | #【模板】链表#

import java.util.*;
public class Main{
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        sc.nextLine();
        MyList myList = new MyList();
        while(sc.hasNextLine()){
            String input = sc.nextLine().trim();
            if(input.equals(""))
                continue;
            String[] arr = input.split(" ");
            if(arr[0].equals("insert"))
                myList.insert(Integer.valueOf(arr[1]),Integer.valueOf(arr[2]));
            else if(arr[0].equals("delete"))
                myList.delete(Integer.valueOf(arr[1]));
        }
        System.out.println(myList);
    }

}
class Node{
    int val;
    Node next;
    public Node(int val){
        this.val = val;
    }
}
class MyList {
    //     Node root=new Node(-1);
    Node root;

    public MyList() {
        root = new Node(-1);
    }

    public void insert(int x, int y) {
        Node xPre = findPre(x);
        Node yNode = new Node(y);
        yNode.next = xPre.next;
        xPre.next = yNode;
    }

    public void delete(int x) {
        Node xPre = findPre(x);
        if (xPre.next != null) {
            xPre.next = xPre.next.next;
        }
    }

    public Node findPre(int x) {//查找节点，如果不存在返回尾节点
        Node cur = root;
        while (cur.next != null && cur.next.val != x) {
            cur = cur.next;
        }
        return cur;
    }

    @Override
    public String toString() {
        StringBuilder sb = new StringBuilder();
        if (root.next == null)
            return "NULL";
        else {
            Node cur = root.next;
            while (cur != null) {
                sb.append(cur.val + " ");
                cur = cur.next;
            }
            return sb.toString();
        }

    }
}

注意： 1.在java中使用class代替了c++的结构体
2.链表可以通过消耗一个变量空间，用来作链表的头结点，方便代码的书写，即使是空链表的插入操作也与其他链表相同。
3.在java中System.out.println()输出Object对象时，会默认调用其toString()，我们可以通过重写toString()修改为自己想要的输出。具体原理如下：

 public void println(Object x) {
        String s = String.valueOf(x);
        synchronized (this) {
            print(s);
            newLine();
        }
    }
    public static String valueOf(Object obj) {
        return (obj == null) ? "null" : obj.toString();
    }