pranay_teja
7/1/2018 - 2:04 PM

Doubly Linked List Implementation

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

// #LinkedList #Class #BasicProblem

class node{
    public:
    node* prev;
    int data;
    node *next;
    node(){ //constructor
        prev=NULL;
        data=0;
        next=NULL;
    }
    node(int x){ //constructor with integer
        prev=NULL;
        data=x;
        next=NULL;
    }
};		//Semicolon after class defn
class ll{
    public:
    node* head;
    ll(){ //constructor
        head=NULL;
    }
    bool isEmpty(); //checks if the ll is empty
    node* getLastNode(); //returns address of the last node of ll
    void printList(); //prints entire ll
    void addAtEnd(int x); //adds an element at the end of ll
    void addAtFront(int x); //adds an element at the front of ll
    void inserter(int x,int n); //inserts x at nth node's position indexing from 1
    node* searcher(int x); //searches for element x and returns its node address
    bool delAtEnd(); //deletes last node and tells if deletion is successfully performed
    bool delAtFront(); //deletes head node and tells if deletion is successfully performed
    bool deleter(int n); //deletes the nth node indexing from 1 and tells if deletion is successfully performed


};
bool ll :: isEmpty(){
    if(head==NULL){
        return true;
    }
    return false;
}
node* ll :: getLastNode(){
    if(head==NULL){
        return head;
    }else{
        node* temp=head;
        while(temp->next!=NULL){
            temp=temp->next;
        }
        return temp;
    }
}
void ll :: printList(){
    if(head==NULL){
        cout<<"List Empty!"<<endl;
    }else{
        node* temp=head;
        while(temp!=NULL){
            cout<<temp->data<<" ";
            temp=temp->next;
        }
    }
    cout<<endl;
}
void ll :: addAtEnd(int x){
    node* n1=new node(x);
    if(head==NULL){
        head=n1;
    }else{
        node* last=getLastNode();
        last->next=n1;
        n1->prev=last;
    }
    //delete(n1); // to delete n1 from memory [DON'T DELETE when ADDing a node]
}
void ll :: addAtFront(int x){
    node* n1=new node(x);
    if(head==NULL){
        head=n1;
    }else{
        head->prev=n1;
        n1->next=head;
        head=n1;
    }
    //delete(n1); // to delete n1 from memory [DON'T DELETE when ADDing a node]
}
void ll ::  inserter(int x,int n){
    if(n==1){
        addAtFront(x);
    }else{
        node* n1=new node(x);
        node* temp=head;
        int pos=2;
        while(pos<n){
            temp=temp->next;
            pos++;
        }
        n1->prev=temp;
        n1->next=temp->next;
        temp->next=n1;
        //delete(n1); // to delete n1 from memory [DON'T DELETE when ADDing a node]
    }
}
node* ll :: searcher(int x){
    node* temp=head;
    int pos=1; //to find position of node is necessary
    while(temp!=NULL){
        if(temp->data==x){
            break;
        }else{
            pos++;
            temp=temp->next;
        }
    }
    return temp;
}
bool ll :: delAtEnd(){
    if(head==NULL){
        return false;
    }else{
        node* temp=head;
        while(temp->next->next!=NULL){
            temp=temp->next;
        }
        node* temp1=temp->next;
        temp->next=NULL;
        delete(temp1); // to delete the last node from memory
        return true;
    }
}
bool ll :: delAtFront(){
    if(head==NULL){
        return false;
    }else{
        node* temp=head;
        head=temp->next;
        delete(temp); // to delete the previous head node from memory
        return true;
    }
}
bool ll :: deleter(int n){
    if(n==1){
        return delAtFront();
    }else{
        int pos=1;
        node* temp=head;
        while(pos<n-1){
            temp=temp->next;
            pos++;
        }
        node* temp1=temp->next;
        temp->next->next->prev=temp;
        temp->next=temp->next->next;
        delete(temp1); // to delete the previous node from memory
        return true;
    }
}
int main(){
    ll l1;
    l1.addAtEnd(2);
    l1.addAtEnd(2);
    l1.addAtEnd(2);
    l1.addAtEnd(2);
    l1.addAtFront(3);
    l1.printList();
    l1.inserter(5,1);
    l1.inserter(5,3);
    l1.printList();
    node * n1=l1.searcher(5);
    cout<<n1->data<<endl;
    if(l1.delAtEnd()==true){
        l1.printList();
    }else{
        cout<<"List Empty!"<<endl;
    }
    if(l1.delAtFront()==true){
        l1.printList();
    }else{
        cout<<"List Empty!"<<endl;
    }
    if(l1.deleter(2)==true){
        l1.printList();
    }else{
        cout<<"List Empty!"<<endl;
    }

    return 0;
}