Remove first node of the linked list

Question

Deletion from beginning in singly linked list 

Answer 1

Python program for deletion of node from beginning in singly linked list

 To delete a node at beginning from linked list,we need to do following steps:

Step:1 Find previous node of the node to be deleted.

Step:2 Changed next of previous node.

Step:3 Free memory for the node to be deleted.

# Node class 

class Node:

    # Function to initialize the node object 

    def __init__(self, data=None, next=None):

        self.data = data # Assign data

        self.next = next # Initialize next as null 

# Linked List class 

class LinkedList:

    # Function to initialize the LinkedList object 

    def __init__(self):

        self.head = None

    # print function prints contents of linked list starting from head

    def print(self):

        # if linked list is empty

        if self.head is None:

            print("Linked list is empty")

            return

        itr = self.head

        #taking empty string and appending values

        llstr = ''

        while itr:

            llstr += str(itr.data)+' --> '

            itr = itr.next

        print(llstr)

    # Function to insert a new node at the beginning

    def insert_at_begining(self, data):

        node = Node(data, self.head)

        self.head = node

       

    #remove first element of the singly linkedlist

    def remove_first(self):

      # if linked list is empty

      if self.head is None:

        print("Empty,nothing to remove") 

        return None

      

      self.head = self.head.next

# Code execution starts here     

if __name__ == '__main__':

    ll = LinkedList()

    

    ll.insert_at_begining("Red")

    ll.insert_at_begining("Green")

    ll.insert_at_begining("Black")

    ll.insert_at_begining("Yellow")

    

    print ("Created Linked List: ")

    ll.print()

    print ("Print Linked List after deletion at first position: ")

    ll.remove_first()

    ll.print()

Output-

Created Linked List:

Yellow --> Black --> Green --> Red --> Print Linked List after deletion at first position:  

Black --> Green --> Red -->