Question

我正在阅读java中的链表，我编写了这段代码，当我运行它时我得到3作为输出，它应该打印出插入数字的相反顺序如下：{{1}我的代码出了什么问题？

10 7 3

由于

Answer 1

您的insert方法未将新节点连接到现有列表的最后一个节点。您必须将新节点分配给现有列表的最后一个节点的node.next：

public void insert(int contents) {

    ListNode newNode = new ListNode(contents);
    if (head == null) {
        head = newNode;
        return;
    }

    ListNode current = head;
    while (current.next != null) {
        current = current.next;
    }

    current.next = newNode;

}

Answer 2

private ListNode head;
private ListNode tail;
public void insert(int contents) {

    ListNode newNode = new ListNode(contents);
    if (head == null) {
        head = newNode;
        tail = newNode;
        return;
    }
    tail.next = newNode;
    tail = newNode;
}

为O（1）插入保留尾节点引用。

您的reverse()方法有点不对：

// this loop will run forever if there are more than 1 nodes
while (nodeNext != null) {
    current.next = null;
    nodeNext.next = current; // you lose the reference to the entire list here
    current = nodeNext;
}

重写功能：

public void reverse() {
    ListNode cursor = head;
    ListNode newHead = null;

    while (cursor != null) {
        ListNode next = cursor.next;
        cursor.next = newHead;
        newHead = cursor;
        cursor = next;
    }
    head = newHead;
}

执行cursor.next = newHead，丢失对cursor.next的原始引用。因此，您需要在临时变量中引用cursor.next：ListNode next = cursor.next;

打印功能

public void print() {
    ListNode cursor = head;
    while (cursor != null) {
        System.out.println(cursor.contents);
        cursor = cursor.next;
    }
}

在java中实现链表

2 个答案: