Python Program For Insertion Sort In A Singly Linked List
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:
Python
# Python implementation of above # algorithm # Node class class Node: # Constructor to initialize the # node object def __init__( self , data): self .data = data self . next = None # Function to sort a singly # linked list using insertion # sort def insertionSort(head_ref): # Initialize sorted linked list sorted = None # Traverse the given linked list # and insert every node to sorted current = head_ref while (current ! = None ): # Store next for next iteration next = current. next # Insert current in sorted # linked list sorted = sortedInsert( sorted , current) # Update current current = next # Update head_ref to point to # sorted linked list head_ref = sorted return head_ref # Function to insert a new_node in a 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()) def sortedInsert(head_ref, new_node): current = None # Special case for the head end if (head_ref = = None or (head_ref).data > = new_node.data): new_node. next = head_ref head_ref = new_node else : # Locate the node before the point # of insertion current = head_ref while (current. next ! = None and current. next .data < new_node.data): current = current. next new_node. next = current. next current. next = new_node return head_ref # Utility Functions # Function to print linked list def printList(head): temp = head while (temp ! = None ): print ( temp.data, end = " " ) temp = temp. next # A utility function to insert a node # at the beginning of linked list def push( head_ref, new_data): # Allocate node new_node = Node( 0 ) # Put in the data new_node.data = new_data # Link the old list off the # new node new_node. next = (head_ref) # Move the head to point to # the new node (head_ref) = new_node return head_ref # Driver code a = None a = push(a, 5 ) a = push(a, 20 ) a = push(a, 4 ) a = push(a, 3 ) a = push(a, 30 ) print ( "Linked List before sorting " ) printList(a) a = insertionSort(a) print ( "Linked List after sorting " ) printList(a) # This code is contributed by Arnab Kundu |
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!