# Linked List Double – Algorithms & Data Structures in C++

#include<iostream>
using namespace std;

/* Linked list structure */
struct list {
struct list *prev;
int data;
struct list *next;
} *node = NULL, *first = NULL, *last = NULL, *node1 = NULL, *node2 = NULL;

class linkedlist {
public:

/* Function for create/insert node at the beginning of Linked list */
void insert_beginning() {
list *addBeg = new list;
cout << “Enter value for the node:” << endl;
cin >> addBeg->data;
if(first == NULL) {
addBeg->prev = NULL;
addBeg->next = NULL;
first = addBeg;
last = addBeg;
cout << “Linked list Created!” << endl;
}
else {
addBeg->prev = NULL;
first->prev = addBeg;
addBeg->next = first;
first = addBeg;
cout << “Data Inserted at the beginning of the Linked list!” << endl;
}
}

/* Function for create/insert node at the end of Linked list */
void insert_end() {
list *addEnd = new list;
cout << “Enter value for the node:” << endl;
cin >> addEnd->data;
if(first == NULL) {
addEnd->prev = NULL;
addEnd->next = NULL;
first = addEnd;
last = addEnd;
cout << “Linked list Created!” << endl;
}
else {
addEnd->next = NULL;
last->next = addEnd;
addEnd->prev = last;
last = addEnd;
cout << “Data Inserted at the end of the Linked list!” << endl;
}
}

/* Function for Display Linked list */
void display() {
node = first;
cout << “List of data in Linked list in Ascending order!” << endl;
while(node != NULL) {
cout << node->data << endl;
node = node->next;
}
node = last;
cout << “List of data in Linked list in Descending order!” << endl;
while(node != NULL) {
cout << node->data << endl;
node = node->prev;
}
}

/* Function for delete node from Linked list */
void del() {
int count = 0, number, i;
node = node1 = node2 = first;
for(node = first; node != NULL; node = node->next)
cout << “Enter value for the node:” << endl;
count++;
display();
cout << count << ” nodes available here!” << endl;
cout << “Enter the node number which you want to delete:” << endl;
cin >> number;
if(number != 1) {
if(number < count && number > 0) {
for(i = 2; i <= number; i++)
node = node->next;
for(i = 2; i <= number-1; i++)
node1 = node1->next;
for(i = 2; i <= number+1; i++)
node2 = node2->next;
node2->prev = node1;
node1->next = node2;
node->prev = NULL;
node->next = NULL;
node = NULL;
}
else if(number == count) {
node = last;
last = node->prev;
last->next = NULL;
node = NULL;
}
else
cout << “Invalid node number!” << endl;
}
else {
node = first;
first = node->next;
first->prev = NULL;
node = NULL;
}
cout << “Node has been deleted successfully!” << endl;
}

};

int main() {
int op = 0;
linkedlist llist = linkedlist();
while(op != 4) {
cout << “1. Insert at the beginning\n2. Insert at the end\n3. Delete\n4. Display\n5. Exit” << endl;
cout << “Enter your choice:” << endl;
cin >> op;
switch(op) {
case 1:
llist.insert_beginning();
break;
case 2:
llist.insert_end();
break;
case 3:
llist.del();
break;
case 4:
llist.display();
break;
case 5:
cout << “Bye Bye!” << endl;
return 0;
break;
default:
cout << “Invalid choice!” << endl;
}
}
return 0;
}