Javascript Program For Insertion Sort In A Singly Linked List

Last Updated : 05 Jan, 2022

We have discussed Insertion Sort for arrays. In this article we are going to discuss Insertion Sort for linked list.
Below is a simple insertion sort algorithm for a linked list.

1) Create an empty sorted (or result) list.
2) Traverse the given list, do following for every node.
......a) Insert current node in sorted way in sorted or result list.
3) Change head of given linked list to head of sorted (or result) list.

The main step is (2.a) which has been covered in the post Sorted Insert for Singly Linked List
Below is implementation of above algorithm:

Javascript

<script>
// Javascript program to sort link list
// using insertion sort
var head = null;
var sorted = null;
  
class node 
{
    constructor(val) 
    {
        this.val = val;
        this.next = null;
    }
}
       
function push(val) 
{
    // Allocate node 
    var newnode = new node(val);
          
    // Link the old list off the 
    // new node 
    newnode.next = head;
          
    // Move the head to point to 
    // the new node 
    head = newnode;
}
  
// Function to sort a singly linked list 
// using insertion sort
function insertionSort(headref) 
{
    // Initialize sorted linked list
    var sorted = null;
    var current = headref;
  
    // Traverse the given linked list 
    // and insert every node to sorted
    while (current != null) 
    {
        // Store next for next iteration
        var next = current.next;
              
        // Insert current in sorted 
        // linked list
        sortedInsert(current);
  
        // Update current
        current = next;
    }
    // Update head_ref to point to 
    // sorted linked list
    head = sorted;
}
  
/* Function to insert a new_node in a Linked List.
   Note that this function expects a pointer to 
   head_ref as this can modify the head of the 
   input linked list (similar to push()) */
function sortedInsert(newnode) 
{
    // Special case for the head end 
    if (sorted == null || 
        sorted.val >= newnode.val) 
     {
         newnode.next = sorted;
         sorted = newnode;
     } 
     else 
     {
         var current = sorted;
  
         /* Locate the node before the point 
            of insertion */
         while (current.next != null && 
                current.next.val < newnode.val) 
         {
             current = current.next;
         }
         newnode.next = current.next;
         current.next = newnode;
     }
}
  
// Function to print linked list 
function printlist(head) 
{
    while (head != null) 
    {
        document.write(head.val + " ");
        head = head.next;
    }
}
  
// Driver code 
push(5);
push(20);
push(4);
push(3);
push(30);
document.write(
"Linked List before Sorting..<br/>");
printlist(head);
insertionSort(head);
document.write(
"<br/>LinkedList After sorting<br/>");
printlist(sorted);
// This code is contributed by aashish1995 
</script>

Output:

Linked List before sorting
30  3  4  20  5
Linked List after sorting
3  4  5  20  30

Please refer complete article on Insertion Sort for Singly Linked List for more details!

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Javascript Program For Insertion Sort In A Singly Linked List

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