Skip to main content

Linked List Data Structure | Insertion at the beginning

Introduction:
In this tutorial we are going to insert a new node at the beginning of the linked list.
There are two important point: first we should have a list and then we have to create a new node.

After creating the linked list and new node we will try to link our new node at the beginning of the list.


code for creating a list:

step1:
For creating the list first of all let's declare the structure of Nodes of the list:

struct Node{
int val;
struct Node *next;
};

step2: write main function:

int main(){

    int n;
    cout<<"enter the number of Nodes:";
    cin>>n;
    struct Node* head = NULL;
    struct Node* temp;
    int m;
    while(n--){
        cout<<"enter the data into nodes:";
        cin>>m;
        if(head==NULL){
            head = new Node();//creating a node
            head->val = m; // assigning value
            head->next=NULL;
            temp=head;//updating temp
        }
        else{
        struct Node *temp1 = new Node();//creating a node
        temp1->val = m;//assigning value
        temp1->next = NULL;
        temp->next = temp1; // linking temp with newly created node(temp1)
        temp=temp1;// shifting temp to newly created node(temp1)
        }
    }
 
}

now we have our list. second step is to create a new node. let's named it "newNode"

struct Node *newNode = new Node(); // after writing this line we have a new node.
newNode->val=7; //let's insert 7 in the value part of this node.
newNode->next = NULL;





Till now we have our linked list and we have our new node. now let's try to insert our newly created node at the beginning of the list.

what we have to do is, in the next field of our newly created node we have to put the address of the head of our linked list(cause head is the first node of the list).

newNode->next = head; // this piece of code will put the address of head node into the next field of newly created node. and this(newNode) will become the first node of the list. and we know that first node should be head. so we will make our newNode head of the list.



head=newNode; // this means now newnode will act as the head of the list.




full code:

#include<bits/stdc++.h>
using namespace std;

struct Node{
int val;
struct Node *next;
};

int main(){

    int n;
    cout<<"enter the number of Nodes:";
    cin>>n;
    struct Node* head = NULL;
    struct Node* temp;
    int m;
    while(n--){
        cout<<"enter the data into nodes:";
        cin>>m;
        if(head==NULL){
            head = new Node();//creating a node
            head->val = m; // assigning value
            head->next=NULL;
            temp=head;//updating temp
        }
        else{
        struct Node *temp1 = new Node();//creating a node
        temp1->val = m;//assigning value
        temp1->next = NULL;
        temp->next = temp1; // linking temp with newly created node(temp1)
        temp=temp1;// shifting temp to newly created node(temp1)
        }
    }

// till now we have created our list. after this we will create our new node .


struct Node *newNode = new Node(); // after writing this line we have a new node.
newNode->val=7; //let's insert 7 in the value part of this node.
newNode->next = NULL;

//now we have our new node also. so let's link it with the list.

newNode->next = head; // this piece of code will put the address of head node into the next field of newly created node.

head = newNode;// this means now newnode will act as the head of the list.

}

so in this post we have created our linked list, we create a new node and then this new node is inserted at the beginning of the list.

if you have any query please comment it down.

best of luck.

next tutorial:


Comments

Post a Comment

Popular posts from this blog

Disjiont Set Union-Find Data Structure | Code In C++

 Introduction:  In this tutorial we are going to write full program of disjoint set union find advance data structure in c++.  Problem Description: Disjoint Set Union (DSU) is an advance data structure, which basically uses in graph algorithms to find cycles. Codes:  Method1: Brute Force #include<bits/stdc++.h> using namespace std; int find(int f,vector<int>&dsuf){     if(dsuf[f]==-1)         return f;     return find(dsuf[f],dsuf); } void union_op(int from, int to, vector<int>& dsuf){     dsuf[from]=to; } bool isCycle(vector<pair<int,int> >&edge_list, vector<int>&dsuf){     for(int i=0;i<edge_list.size();i++){         int parent1=find(edge_list[i].first,dsuf);         int parent2=find(edge_list[i].second,dsuf);         if(parent1==pare...
Post a Comment
Read more

Linked List Data Structure | Add Two Number Explanation

Introduction: In this tutorial, we are going to solve a very famous problem on Linked List. It is also an important question for coding interview. so let's see the problem and understand it in detail. Problem Statement: There are two numbers and each digit of number is represented by a node of linked list.and we have to add these two numbers, which is given in the form of linked list. Input: (2 -> 4 -> 3) + (5 -> 6 -> 4) Output: 7 -> 0 -> 8 eg: num1 = 2354;       num2 = 875; see the image below: Solution: Now let's solve it. In this problem there may be three possibilities. First: Number of Nodes in the first linked list is greater than second linked list. Second: Number of Nodes in first linked list is less than second list. Third: Number of Nodes in the both linked list is equal. Here number of nodes means number of digits in both number. Another thing we have to keep in mind is that if we add two digits then there may be possibility of gen...
Post a Comment
Read more

Integrating Frontend to Backend | MERN stack(100% working)

How to Integrate frontend to backend in MERN stack? For integrating the frontend to backend just do two things. Step1: Go and install cors on both side (front end as well as backend)              To install cors simply open the folder into terminal and type npm install cors--save. step 2: just go to your front end section(react app) open package.json file.                 and just add one line into package.json file.           "proxy":"http://localhost:4000" here i am using 4000, so what is 4000 ?. this is the port  on which our backend is listening. so it may be possible that u may have other port number on which your server is listening. so put yours port number on which your backend server is listening. and this proxy thing we have to add in frontend part not in backend part. Now it may be possible that you want to know ...
Post a Comment
Read more