递归插入双向链表的末尾 [英] Recursively insert at the end of doubly linked list

问题描述

我有一个双向链接列表，我想递归在列表末尾插入一个元素。我现在有一个方法可以做到这一点而无需递归，并且可以正常工作。我似乎无法理解如何使用递归。我认为，在带有递归的单链接列表的末尾插入是很容易理解的，因此，我希望有人可以解释在双链接列表时如何执行此操作。这是我想递归的普通插入方法：

I have a doubly linked list, and I want to insert an element at the end of the list recursively. I have a method now that does this without recursion, and it works. I just can't seem to understand how to do it with recursion. Inserting at the end of a singly linked list with recursion is quite easy to understand I think, so I hope that someone can explain how to it do it when the list is doubly linked. Here is my normal insertion method that I want to make recursive:

public void insert(T element) {
    Node in = new Node(element);

    if (in == null) {
        first = in;
    } else {
        Node tmp = first;
        while (tmp.next != null) {
            tmp = tmp.next;
        }
        tmp.next = in;
        in.prec = tmp;
    }
}

推荐答案

想法只是用函数调用重写while循环：

The idea is just to re-write the while loop with a function call:

public void insert(T element) {
    insert(element, first);    // initialization
}

private void insert(T e, Node n) {
    if(n == null) {            // if the list is empty
        first = new Node(e);
    } else if(n.next == null) {       // same condition as in the while loop
        None newNode = new Node(e);
        n.next = newNode;
        newNode.prec = n;
    } else {
        insert(e, n.next);    // looping
    }
}

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