Java刷题实现链表问题

Question

Java刷题实现链表问题

是这样的，我在lc上面刷题。写链表题目的时候只能在lc上面提交，因为lc上面有提供ListNode

这就只能在lc上面写题目了，遇到问题调试要开会员，我就想在本地写一个ListNode，然后写题目这样还能调试代码。这是我写的ListNode

public class ListNode {
    public int value;
    public ListNode next;

    public ListNode(int value) {
        this.value = value;
    }

    public ListNode(int value, ListNode next) {
        this.value = value;
        this.next = next;
    }

    public ListNode head;

    public ListNode() {
        this.head = null;
    }

    // 添加节点
    public void append(int value) {
        ListNode newNode = new ListNode(value);
        if (head == null) {
            head = newNode;
            return;
        }
        ListNode last = head;
        while (last.next != null) {
            last = last.next;
        }

        last.next = newNode;
    }
    // 打印遍历
    public void printList() {
        ListNode current = head;
        while (current != null) {
            System.out.print(current.value + " ");
            current = current.next;
        }
        System.out.println();
    }

试过了添加和打印遍历都是没有问题的，但是用来写题目遍历出来的都不是正确答案，但是在lc上面还是正确提交的比如这道
合并两个有序链表

private static ListNode mergeTwoLists(ListNode list1, ListNode list2) {
        if (list1 == null) {
            return list2;
        }
        if (list2 == null) {
            return list1;
        }
        if (list1.value < list2.value) {
            list1.next = mergeTwoLists(list1.next, list2);
            return list1;
        } else {
            list2.next = mergeTwoLists(list1, list2.next);
            return list2;
        }
    }

main方法

public static void main(String[] args) {
        ListNode list1 = new ListNode();

        list1.append(1);
        list1.append(2);
        list1.append(4);

       System.out.print("list1: "); list1.printList();

        ListNode list2 = new ListNode();

        list2.append(1);
        list2.append(3);
        list2.append(4);

        System.out.print("list2: "); list2.printList();

        System.out.println("=======================");

        mergeTwoLists(list1, list2).printList();

    }

输出结果

个人推测可能是ListNode有啥问题，希望各位可以指点

Answer 1

public class ListNode {
    public int value;
    public ListNode next;
    public ListNode(int value) {
        this.value = value;
    }
    public ListNode(int value, ListNode next) {
        this.value = value;
        this.next = next;
    }
    //public ListNode head;
    public ListNode() {
    //    this.head = null;
    }
    // 添加节点
    public void append(int value) {
        ListNode newNode = new ListNode(value);
        if (next == null) {
            next = newNode;
            return;
        }
        ListNode last = this;
        while (last.next != null) {
            last = last.next;
        }
        last.next = newNode;
    }
    // 打印遍历
    public void printList() {
        ListNode current = this;
        while (current != null) {
            System.out.print(current.value + " ");
            current = current.next;
        }
        System.out.println();
    }
private static ListNode mergeTwoLists(ListNode list1, ListNode list2) {
        if (list1 == null) {
            return list2;
        }
        if (list2 == null) {
            return list1;
        }
        if (list1.value < list2.value) {
            list1.next = mergeTwoLists(list1.next, list2);
            return list1;
        } else {
            list2.next = mergeTwoLists(list1, list2.next);
            return list2;
        }
    }
public static void main(String[] args) {
        ListNode list1 = new ListNode(1);
        //list1.append(1);
        list1.append(2);
        list1.append(4);
        System.out.print("list1: "); list1.printList();
        ListNode list2 = new ListNode(1);
        //list2.append(1);
        list2.append(3);
        list2.append(4);
        System.out.print("list2: "); list2.printList();
        System.out.println("=======================");
        mergeTwoLists(list1, list2).printList();
    }
}