C++ - 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.
void push_front(int newElement) {
//1. allocate a new node
Node* newNode = new Node();
//2. assign data element
newNode->data = newElement;
//3. make next node of new node as head
newNode->next = head;
//4. make new node as head
head = newNode;
}
The below is a complete program that uses above discussed concept to insert new node at the start of the linked list.
#include <iostream>
using namespace std;
//node structure
struct Node {
int data;
Node* next;
};
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 = 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
