JavaScript 以N个节点为单位旋转双向链表

双向链表是一种线性数据结构，每个节点存储着下一个节点和前一个节点的地址。给定一个双向链表，我们需要以N个节点为单位旋转链表并将其打印出来。这里的N是一个正数，且小于等于链表中节点的数量。

我们没有给定具体旋转的方向，所以我们会同时按照两个方向旋转链表。

逆时针旋转双向链表

我们需要将双向链表的节点逆时针旋转给定的次数（N）。对于位于链表边缘的节点，它们将除了最后一个节点之外的所有节点都向右旋转，假设将双向链表看作一个循环，然后将最后一个节点移动到第一个节点或头部位置。我们将实现一个合适的算法来实现这个操作，并给出解释。

示例

假设我们有一个双向链表：

LL = [1, 2, 3, 4, 5, 6, 7]

节点旋转次数为3

输出：

旋转后的LL = [5, 6, 7, 1, 2, 3, 4]

示例

在下面的示例中，我们将一个双向链表逆时针旋转3次。

输入：1 <=> 2 <=> 3 <=> 4 <=> 5 <=> 6 <=> 7 <=> 8 -> null

期望输出：6 <=> 7 <=> 8 <=> 1 <=> 2 <=> 3 <=> 4 <=> 5 -> null

// class to create the structure of the nodes
class Node{
   constructor(data) {
      this.value = data;
      this.next = null;
      this.prev = null;
   }
}

// function to print the linked list
function print(head){
   var temp = head;
   var ans = ""
   while(temp.next != null){
      ans += temp.value;
      ans += " <=> "
      temp = temp.next
   }
   ans += temp.value
   ans += " -> null"
   console.log(ans)
}

// function to add data in linked list
function add(data, head, tail){
   var new_node = new Node(data);
   if(head == null){
      head = new_node
      return new_node
   }
   else{
      tail.next = new_node;
      new_node.prev = tail
      return new_node
   }
}

// function to rotate the linked list
function rotate(head, rotations){
   var temp = head;

   // getting length of the linked list
   var len = 0;
   while(temp != null){
      len++;
      temp = temp.next;
   }
   temp = head;
   var mid = temp;
   for(var i=0;i<len-rotations;i++){
      mid = mid.next;
   }
   mid.prev.next = null
   head = mid
   head.prev = null
   while(mid.next != null){
      mid = mid.next;
   }
   mid.next = temp;
   return head;
}

// defining linked list
var head = new Node(1)
var tail = head
tail = add(2,head, tail)
tail = add(3,head, tail)
tail = add(4,head, tail)
tail = add(5,head, tail)
tail = add(6,head, tail)
tail = add(7,head, tail)
tail = add(8,head, tail)
// given number
number = 3;
console.log("The given linked list is: ")
print(head)
console.log("The given linked list after 3 rotations is: ")
head = rotate(head,number)
print(head)

输出

The given linked list is: 
1 <=> 2 <=> 3 <=> 4 <=> 5 <=> 6 <=> 7 <=> 8 -> null
The given linked list after 3 rotations is: 
6 <=> 7 <=> 8 <=> 1 <=> 2 <=> 3 <=> 4 <=> 5 -> null

将双向链表顺时针旋转

我们需要将双向链表的节点顺时针旋转给定的次数（N）次。对于位于边缘的节点，它们将在右旋转时移到循环形式的双向链表的第一个索引。我们将实现一段合适的代码，以解释算法。

示例：

假设我们有一个双向链表：

LL = [1, 2, 3, 4, 5, 6, 7]

旋转的次数为3

输出：

旋转后的LL = [4, 5, 6, 7, 1, 2, 3]

示例

在下面的示例中，我们将一个双向链表顺时针旋转3次。

输入：1 <=> 2 <=> 3 <=> 4 <=> 5 <=> 6 <=> 7 <=> 8 -> null

预期输出：4 <=> 5 <=> 6 <=> 7 <=> 8 <=> 1 <=> 2 <=> 3 -> null

// class to create the structure of the nodes
class Node{
   constructor(data){
      this.value = data;
      this.next = null;
      this.prev = null;
   }
}
// function to print the linked list
function print(head){
   var temp = head;
   var ans = ""
   while(temp.next != null){
      ans += temp.value;
      ans += " <=> "
      temp = temp.next
   }
   ans += temp.value
   ans += " -> null"
   console.log(ans)
}
// function to add data in linked list
function add(data, head, tail){
   var new_node = new Node(data);
   if(head == null){
      head = new_node
      return new_node
   }
   else{
      tail.next = new_node;
      new_node.prev = tail
      return new_node
   }
}
// function to rotate the linked list
function rotate(head, rotations){
   var temp = head;
   // getting length of the linked list
   var len = 0;
   while(temp != null){
      len++;
      temp = temp.next;
   }
   temp = head;
   var mid = temp;
   for(var i=0;i<rotations;i++){
      mid = mid.next;
   }
   mid.prev.next = null
   head = mid
   head.prev = null
   while(mid.next != null){
      mid = mid.next;
   }
   mid.next = temp;
   return head;
}
// defining linked list
var head = new Node(1)
var tail = head
tail = add(2,head, tail)
tail = add(3,head, tail)
tail = add(4,head, tail)
tail = add(5,head, tail)
tail = add(6,head, tail)
tail = add(7,head, tail)
tail = add(8,head, tail)
// given number
number = 3;
console.log("The given linked list is: ")
print(head)
console.log("The given linked list after 3 rotations is: ")
head = rotate(head, number)
print(head)

输出

The given linked list is: 
1 <=> 2 <=> 3 <=> 4 <=> 5 <=> 6 <=> 7 <=> 8 -> null
The given linked list after 3 rotations is: 
4 <=> 5 <=> 6 <=> 7 <=> 8 <=> 1 <=> 2 <=> 3 -> null