Insertion of node at beginning(front) in DLL

Front Insertion of node is very easy in Doubly Singly Linked List(DLL). we have to apply some basic node arrangement.

• First we need one new node for inserting, So allocate the memory for new node.
• and then insert the new node at beginning of DLL.

Working Process

Code Implementation

#include <stdio.h>
#include <iostream>
#include<conio.h>
#include<math.h>
#include<stdlib.h>
struct CreateNode   // Node Structure Initialization
{
	int  data;          // for data element
	struct CreateNode* nextNode;   //for storing the address of next element
	struct CreateNode* prevNode;   //for storing the address of Previous element
};
struct CreateNode *HeadPointer = NULL;    // Initialization of HeadPointer

void insertNodeAtFrontInDLL(int data)   // Method of front Addition
{
	//Memory Initialization for NewNode
	struct CreateNode* NewNode = (struct CreateNode *)malloc(sizeof(struct CreateNode *));
	if (NewNode != NULL)
	{
		if (HeadPointer == NULL)
		{
			NewNode->data = data;
			HeadPointer = NewNode;
			NewNode->nextNode = NULL;
			NewNode->prevNode = NULL;
			printf("NewNode has been added...\n");
		}
		else
		{
			NewNode->data = data;
			HeadPointer->prevNode = NewNode;
			NewNode->nextNode = HeadPointer;
			NewNode->prevNode = NULL;
			HeadPointer = NewNode;
			printf("NewNode has been added...\n");
		}
	}
	else
	{
		printf("Memory is not Initialized for NewNode.");
	}
}
int main()
{
	int data, choice;
	do
	{
		printf("Enter the data for insertion :");
		std::cin >> data;
		insertNodeAtFrontInDLL(data);
		printf("Press 0 for more insertion :");
		std::cin >> choice;
	} while (choice == 0);
	struct CreateNode* Temp = HeadPointer;
	printf("Node data after insertion process :\n");
	while (Temp->nextNode != NULL)
	{
		printf("%d ", Temp->data);
		Temp = Temp->nextNode;
	}
	printf("%d ", Temp->data);
	_getch();
	return 0;
}

Time & Space Complexity

• Time Complexity will be O(1).
• Space Complexity will be O(1).