用N个节点旋转双向链表的Javascript程序

给定一个双向链表，将链表逆时针旋转 N 个节点。这里 N 是给定的正整数，并且小于链表中的节点数。

N = 2
轮换名单：

例子：

Input : a  b  c  d  e   N = 2
Output : c  d  e  a  b 

Input : a  b  c  d  e  f  g  h   N = 4
Output : e  f  g  h  a  b  c  d 

在亚马逊上问

要旋转双向链表，我们需要将第 N 个节点的下一个节点更改为 NULL，将最后一个节点的下一个节点更改为前一个头节点，将头节点的 prev 更改为最后一个节点，最后将 head 更改为第 (N+1) 个节点和 prev新的头节点为 NULL（双向链表中头节点的上一个为 NULL）
所以我们需要掌握三个节点：第 N 个节点、第 (N+1) 个节点和最后一个节点。从开始遍历列表并在第 N 个节点处停止。存储指向第 N 个节点的指针。我们可以使用 NthNode->next 获得第 (N+1) 个节点。继续遍历直到结束并存储指向最后一个节点的指针。最后，如上所述更改指针，并在 Last Print Rotated List 使用
打印列表函数。

Javascript

// javascript program to rotate a Doubly linked
// list counter clock wise by N times
 
    /* Link list node */
     class Node {
            constructor() {
                this.data = 0;
                this.prev = null;
                this.next = null;
            }
        }
    var head = null;
 
    // This function rotates a doubly linked
    // list counter-clockwise and updates the
    // head. The function assumes that N is
    // smallerthan size of linked list. It
    // doesn't modify the list if N is greater
    // than or equal to size
    function rotate(N) {
        if (N == 0)
            return;
 
        // Let us understand the below code
        // for example N = 2 and
        // list = a <-> b <-> c <-> d <-> e.
var current = head;
 
        // current will either point to Nth
        // or NULL after this loop. Current
        // will point to node 'b' in the
        // above example
        var count = 1;
        while (count < N && current != null) {
            current = current.next;
            count++;
        }
 
        // If current is NULL, N is greater
        // than or equal to count of nodes
        // in linked list. Don't change the
        // list in this case
        if (current == null)
            return;
 
        // current points to Nth node. Store
        // it in a variable. NthNode points to
        // node 'b' in the above example
var NthNode = current;
 
        // current will point to last node
        // after this loop current will point
        // to node 'e' in the above example
        while (current.next != null)
            current = current.next;
 
        // Change next of last node to previous
        // head. Next of 'e' is now changed to
        // node 'a'
        current.next = head;
 
        // Change prev of Head node to current
        // Prev of 'a' is now changed to node 'e'
        (head).prev = current;
 
        // Change head to (N+1)th node
        // head is now changed to node 'c'
        head = NthNode.next;
 
        // Change prev of New Head node to NULL
        // Because Prev of Head Node in Doubly
        // linked list is NULL
        (head).prev = null;
 
        // change next of Nth node to NULL
        // next of 'b' is now NULL
        NthNode.next = null;
    }
 
    // Function to insert a node at the
    // beginning of the Doubly Linked List
    function push( new_data) {
var new_node = new Node();
        new_node.data = new_data;
        new_node.prev = null;
        new_node.next = (head);
        if ((head) != null)
            (head).prev = new_node;
        head = new_node;
    }
 
    /* Function to print linked list */
    function printList(node) {
        while (node != null && node.next != null) {
            document.write(node.data + " ");
            node = node.next;
        }
        if (node != null)
            document.write(node.data);
    }
 
    // Driver's Code
     
        /* Start with the empty list */
        // Node head = null;
 
        /*
         * Let us create the doubly linked list a<->b<->c<->d<->e
         */
        push('e');
        push('d');
        push('c');
        push('b');
        push('a');
 
        var N = 2;
 
        document.write("Given linked list <br/>");
        printList(head);
        rotate(N);
        document.write();
        document.write("<br/>Rotated Linked list <br/>");
        printList(head);
 
// This code contributed by aashish1995

输出：

Given linked list 
a  b  c  d  e
Rotated Linked list 
c  d  e  a  b

更多详细信息请参考完整文章旋转 N 个节点的双向链表！