insertioninDLL.cpp

/*Author : KRISH JHA */
/*scholar id : 2312119*/

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

class Node{

    public :
    int data;
    Node* next;
    Node* prev;

    Node(int data){
        this -> data = data;
        this -> next = NULL;
        this -> prev = NULL;
    }
};

void prepend(Node* &head , int data){

    Node* newNode = new Node(data);

    newNode -> next = head;
    if(head != NULL){
        head -> prev = newNode;
    }

    head = newNode;
}

void append(Node* &head , int data){

    Node* newNode = new Node(data);

    if(head == NULL){
        head = newNode;
    }
    else{
        Node* temp = head;
        while(temp -> next){
            temp = temp -> next;
        }

        temp -> next = newNode;
        newNode -> prev = temp;
    }
}

void insertAtk(Node* &head , int pos , int data){

    Node* newNode = new Node(data);

    if(pos == 1){
        prepend(head , data);
    }
    else{
        Node* temp = head;
        int cnt = 1;
        while(temp != NULL && cnt != pos - 1){
            temp = temp -> next;
        }

        newNode -> prev = temp;
        newNode -> next = temp -> next;
        temp -> next = newNode;
        newNode -> next -> prev = newNode;
    }
}

void printDLL(Node* &head){

    Node* temp = head;
    
    while(temp != NULL){
        cout << temp -> data << ' ';
        temp = temp -> next;
    }

    cout << endl;
}
int main() {

    #ifndef ONLINE_JUDGE
    freopen("input1.txt", "r", stdin);
    freopen("output1.txt", "w", stdout);
    #endif

    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    
    Node* head = new Node(1);
    printDLL(head);

    prepend(head , 2);
    printDLL(head);

    append(head , 3);
    printDLL(head);
    
    insertAtk(head , 2 , 4);
    printDLL(head);

    return 0;
    
}