Python - Delete the first node of the Doubly Linked List
In this method, the first node of the doubly linked list is deleted. For example - if the given list is 10->20->30->40 and the first node is deleted, the list becomes 20->30->40.
Deleting the first node of the Doubly Linked List is very easy. If the head is not null then create a temp node pointing to head and move head to the next of head. Then delete the temp node. If the new head is not null, make the prev of it as null.
The function pop_front is created for this purpose. It is a 4-step process.
def pop_front(self): if(self.head != None): #1. if head is not null, create a # temp node pointing to head temp = self.head; #2. move head to next of head self.head = self.head.next; #3. delete temp node temp = None; #4. If the new head is not null, then # make prev of the new head as null if(self.head != None): self.head.prev = None
The below is a complete program that uses above discussed concept of deleting the first node of the doubly linked list.
# node structure class Node: def __init__(self, data): self.data = data self.next = None self.prev = None #class LinkedList class LinkedList: def __init__(self): self.head = None #Add new element at the end of the list def push_back(self, newElement): newNode = Node(newElement) if(self.head == None): self.head = newNode return else: temp = self.head while(temp.next != None): temp = temp.next temp.next = newNode newNode.prev = temp #Delete first node of the list def pop_front(self): if(self.head != None): temp = self.head; self.head = self.head.next; temp = None; if(self.head != None): self.head.prev = None #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 four elements in the list. MyList.push_back(10) MyList.push_back(20) MyList.push_back(30) MyList.push_back(40) MyList.PrintList() #Delete the first node MyList.pop_front() MyList.PrintList()
The above code will give the following output:
The list contains: 10 20 30 40 The list contains: 20 30 40