Insertion at Beginning in Singly Linked List in C++
How to perform insertion at the beginning in Linked List in C++?
Insertion at Beginning in Linked List in C++ is one of the operations that we can perform on Linked List. linked list in C++ is part of a linked list and is a type of linear data structure. Linked is made up of two parts node and pointer where node contains the data and pointer contains the address of the next node.
Linked list definition in C++
Nodes of a linked list are created by using the code mentioned besides.
This set of codes will construct a linked list by creating each node of the list.
class Node
{
int data;
Node *next;
}; Steps to insert an element at beginning of linked list
- Allocate space for a new node.
- ptr = (struct node *) malloc(sizeof(struct node *));
- In the space created for new node put the data in.
- new_node->data = new_data
- Point the pointer of new node to the head of the linked list
- new_node->ptr = (*head);
- Make new node as head
- (*head) = new_node
Linked List
We can traverse in only one direction in linked list as linked list does not contain previous pointer, it only has next pointer.
C++ program to insert an element at beginning of linked list
Method 1
Method 2
Method 1
Using non-member functions and passing head explicitly
Run
#include<iostream>
using namespace std;
class Node
{
public:
int data;
Node *next;
};
void insertFront(Node** head, int data){
Node* new_node = new Node();
// assign data
new_node->data = data;
// change the next node of this newNode
// to current head of Linked List
new_node->next = *head;
// new_node should become the new head of Linked List
*head = new_node;
cout << "Inserted Item: " << new_node->data << endl;
}
void printList(Node* node){
cout << "\nLinked List : " ;
//as linked list will end when Node is Null
while(node!=NULL){
cout << node->data << " "; node = node->next;
}
cout << endl;
}
int main(){
Node* head = NULL;
insertFront(&head,4);
insertFront(&head,5);
insertFront(&head,6);
insertFront(&head,7);
insertFront(&head,8);
insertFront(&head,9);
printList(head);
return 0;
}
Output
Inserted Item: 4 Inserted Item: 5 Inserted Item: 6 Inserted Item: 7 Inserted Item: 8 Inserted Item: 9 Linked List : 9 8 7 6 5 4
Method 2
Using member functions and using head member variable
Run
#include<iostream>
using namespace std;
class Node
{
public:
int data;
Node *next;
};
class LinkedList
{
private:
Node* head;
public:
LinkedList() { // constructor
head = NULL;
}
void insertFront(int data);
void printList();
};
void LinkedList::insertFront(int data){
Node* new_node = new Node();
// assign data value
new_node->data = data;
// change the next node of this new_node
// to current head of Linked List
new_node->next = head;
// new_node should become the new head of Linked List
head = new_node;
cout << "Inserted Item: " << new_node->data << endl;
}
void LinkedList::printList(){
Node* node = new Node();
node = head;
cout << "\nLinked List : " ;
//as linked list will end when Node is Null
while(node!=NULL){
cout << node->data << " "; node = node->next;
}
cout << endl; } int main() { LinkedList* new_list = new LinkedList(); new_list->insertFront(4);
new_list->insertFront(5);
new_list->insertFront(6);
new_list->insertFront(7);
new_list->insertFront(8);
new_list->insertFront(9);
new_list->printList();
return 0;
}Output
Inserted Item: 4 Inserted Item: 5 Inserted Item: 6 Inserted Item: 7 Inserted Item: 8 Inserted Item: 9 Linked List : 9 8 7 6 5 4
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