# C++ - Insert a new node at the start of the Doubly Linked List

In this method, a new node is inserted at the start of the doubly linked list. For example - if the given List is 10->20->30 and a new element 100 is added at the start, the List becomes 100->10->20->30.

Inserting a new node at the start of the doubly linked list is very easy. First, a new node with given element is created. It is then added at the start of the list by linking the head node to the new node.

The function *push_front* is created for this purpose. It is a **5-step process**.

void push_front(int newElement) { //1. allocate node Node* newNode = new Node(); //2. assign data element newNode->data = newElement; //3. assign null to the next and prev // of the new node newNode->next = NULL; newNode->prev = NULL; //4. Check the list is empty or not, // if empty make the new node as head if(head == NULL) { head = newNode; } else { //5. Adjust the links and make the new // node as head head->prev = newNode; newNode->next = head; head = newNode; } }

The below is a complete program that uses above discussed concept to insert new node at the start of the doubly linked list.

#include <iostream> using namespace std; //node structure struct Node { int data; Node* next; Node* prev; }; class LinkedList { private: Node* head; public: LinkedList(){ head = NULL; } //Add new element at the start of the list void push_front(int newElement) { Node* newNode = new Node(); newNode->data = newElement; newNode->next = NULL; newNode->prev = NULL; if(head == NULL) { head = newNode; } else { head->prev = newNode; newNode->next = head; head = newNode; } } //display the content of the list void PrintList() { Node* temp = head; if(temp != NULL) { cout<<"The list contains: "; while(temp != NULL) { cout<<temp->data<<" "; temp = temp->next; } cout<<endl; } else { cout<<"The list is empty.\n"; } } }; // test the code int main() { LinkedList MyList; //Add three elements at the start of the list. MyList.push_front(10); MyList.push_front(20); MyList.push_front(30); MyList.PrintList(); return 0; }

The above code will give the following output:

The list contains: 30 20 10