Python - Insert a new node at the start of the Linked List
In this method, a new node is inserted at the beginning of the linked list. For example - if the given List is 10->20->30 and a new element 100 is added at the start, the Linked List becomes 100->10->20->30.
Inserting a new node at the beginning of the Linked List is very easy. First, a new node with given element is created. It is then added before the head of the given Linked List that makes the newly added node to new head of the Linked List by changing the head pointer to point to the new node.
The function push_front is created for this purpose. It is a 4-step process.
def push_front(self, newElement): #1 & 2. allocate a new node # and assign data element newNode = Node(newElement) #3. make next node of new node as head newNode.next = self.head #4. make new node as head self.head = newNode
The below is a complete program that uses above discussed concept to insert new node at the start of the linked list.
# node structure class Node: def __init__(self, data): self.data = data self.next = None #class Linked List class LinkedList: def __init__(self): self.head = None #Add new element at the start of the list def push_front(self, newElement): newNode = Node(newElement) newNode.next = self.head self.head = newNode #display the content of the list def PrintList(self): temp = self.head if(temp != None): print("\nThe list contains:", end=" ") while (temp != None): print(temp.data, end=" ") temp = temp.next else: print("\nThe list is empty.") # test the code MyList = LinkedList() #Add three elements at the start of the list. MyList.push_front(10) MyList.push_front(20) MyList.push_front(30) MyList.PrintList()
The above code will give the following output:
The list contains: 30 20 10