通过更改链接对给定链接列表的元素进行成对交换的 Javascript 程序

给定一个单链表，编写一个函数来成对交换元素。例如，如果链表是 1->2->3->4->5->6->7，那么函数应该将其更改为 2->1->4->3->6->5 ->7，如果链表是 1->2->3->4->5->6，那么函数应该将其更改为 2->1->4->3->6->5

这个问题已经在这里讨论过了。那里提供的解决方案交换节点的数据。如果数据包含很多字段，就会有很多交换操作。因此，更改链接通常是一个更好的主意。以下是更改链接而不是交换数据的实现。

Javascript

// Javascript program to swap elements
// of linked list by changing links
var head;
 
class Node
{
    constructor(val)
    {
        this.data = val;
        this.next = null;
    }
}
      
/* Function to pairwise swap elements
   of a linked list */
function pairWiseSwap(node)
{
    // If linked list is empty or there
    // is only one node in list
    if (node == null ||
        node.next == null)
    {
        return node;
    }
 
    // Initialize previous and current
    // pointers
    var prev = node;
    var curr = node.next;
 
    // Change head before proceeding
    node = curr;
 
    // Traverse the list
    while (true)
    {
        var next = curr.next;
 
        // Change next of current as
        // previous node
        curr.next = prev;
 
        // If next NULL or next is the
        // last node
        if (next == null ||
            next.next == null)
        {
            prev.next = next;
            break;
        }
 
        // Change next of previous to next
        // next
        prev.next = next.next;
 
        // Update previous and curr
        prev = next;
        curr = prev.next;
    }
    return node;
}
 
/* Function to print nodes in a
   given linked list */
function printList(node)
{
    while (node != null)
    {
        document.write(node.data + " ");
        node = node.next;
    }
}
 
// Driver code
/* The constructed linked list is:
   1->2->3->4->5->6->7 */
head = new Node(1);
head.next = new Node(2);
head.next.next = new Node(3);
head.next.next.next = new Node(4);
head.next.next.next.next =
new Node(5);
head.next.next.next.next.next =
new Node(6);
head.next.next.next.next.next.next =
new Node(7);
 
document.write(
"Linked list before calling pairwiseSwap() ");
printList(head);
var st = pairWiseSwap(head);
document.write("<br/>");
document.write(
"Linked list after calling pairwiseSwap() ");
printList(st);
document.write("");
// This code is contributed by aashish1995

输出：

Linked list before calling  pairWiseSwap() 1 2 3 4 5 6 7
Linked list after calling  pairWiseSwap() 2 1 4 3 6 5 7

时间复杂度：上述程序的时间复杂度为 O(n)，其中 n 是给定链表中的节点数。 while 循环遍历给定的链表。

辅助空间：O(1)

以下是相同方法的递归实现。我们更改前两个节点并重复剩余列表。感谢 geek 和 omer salem 提出这种方法。

Javascript

// Javascript program to swap elements of
// linked list by changing links
var head;
class Node
{
    constructor(val)
    {
        this.data = val;
        this.next = null;
    }
}
 
/* Function to pairwise swap elements of
   a linked  It returns head of the modified
   list, so return value of this node must be
   assigned */
function pairWiseSwap(node)
{
    // Base Case: The list is empty or has
    // only one node
    if (node == null ||
        node.next == null)
    {
        return node;
    }
 
// Store head of list after
// two nodes
var remaining = node.next.next;
 
// Change head
var newhead = node.next;
 
// Change next of second node
node.next.next = node;
 
// Recur for remaining list and
// change next of head
node.next = pairWiseSwap(remaining);
 
// Return new head of modified list
return newhead;
}
 
/* Function to print nodes in a
   given linked list */
function printList(node)
{
    while (node != null)
    {
        document.write(node.data + " ");
        node = node.next;
    }
}
 
// Driver code
/* The constructed linked list is:
   1->2->3->4->5->6->7 */
head = new Node(1);
head.next = new Node(2);
head.next.next = new Node(3);
head.next.next.next = new Node(4);
head.next.next.next.next =
new Node(5);
head.next.next.next.next.next =
new Node(6);
head.next.next.next.next.next.next =
new Node(7);
 
document.write(
"Linked list before calling pairwiseSwap() ");
printList(head);
head = pairWiseSwap(head);
document.write("<br/>");
document.write(
"Linked list after calling pairwiseSwap() ");
printList(head);
document.write("");
// This code is contributed by umadevi9616

输出：

Linked list before calling  pairWiseSwap() 1 2 3 4 5 6 7
Linked list after calling  pairWiseSwap() 2 1 4 3 6 5 7

时间复杂度：O(n)

辅助空间：O(n)

请通过更改链接来参阅有关给定链接列表的成对交换元素的完整文章以获取更多详细信息！