Single Linked List Program in c++

/*
 * C++ Program to Implement Singly Linked List
 */
#include<iostream>
#include<cstdlib>
using namespace std;
/*
 * Node Declaration
 */
struct node
{
    int info;
    struct node *next;
}*start;

/*
 * Class Declaration
 */
class single_llist
{
    public:
        node* create_node(int);
        void insert_begin();
        void insert_pos();
        void insert_last();
        void delete_pos();
        void search();
        void display();
        single_llist()
        {
            start = NULL;
        }
};

/*
 * Main :contains menu
 */
main()
{
    int choice;// nodes, element, position, i;
    single_llist sl;
    start = NULL;
    while (1)
    {
        cout<<endl<<"---------------------------------"<<endl;
        cout<<endl<<"Operations on singly linked list"<<endl;
        cout<<endl<<"---------------------------------"<<endl;
        cout<<"1.Insert Node at beginning"<<endl;
        cout<<"2.Insert node at last"<<endl;
        cout<<"3.Insert node at position"<<endl;
        cout<<"4.Delete a Particular Node"<<endl;
        cout<<"5.Search Element"<<endl;
        cout<<"6.Display Linked List"<<endl;
        cout<<"7.Exit "<<endl;
        cout<<"Enter your choice : ";
        cin>>choice;
        switch(choice)
        {
        case 1:
            cout<<"Inserting Node at Beginning: "<<endl;
            sl.insert_begin();
            cout<<endl;
            break;
        case 2:
            cout<<"Inserting Node at Last: "<<endl;
            sl.insert_last();
            cout<<endl;
            break;
        case 3:
            cout<<"Inserting Node at a given position:"<<endl;
            sl.insert_pos();
            cout<<endl;
            break;
        case 4:
            cout<<"Delete a particular node: "<<endl;
            sl.delete_pos();
            break;
        case 5:
            cout<<"Search element in Link List: "<<endl;
            sl.search();
            cout<<endl;
            break;
        case 6:
            cout<<"Display elements of link list"<<endl;
            sl.display();
            cout<<endl;
            break;
        case 7:
            cout<<"Exiting..."<<endl;
            exit(1);
            break;
        default:
            cout<<"Wrong choice"<<endl;
        }
    }
}

/*
 * Creating Node
 */
node *single_llist::create_node(int value)
{
    struct node *temp, *s;
    temp = new(struct node);
    if (temp == NULL)
    {
        cout<<"Memory not allocated "<<endl;
        return 0;
    }
    else
    {
        temp->info = value;
        temp->next = NULL;    
        return temp;
    }
}

/*
 * Inserting element in beginning
 */
void single_llist::insert_begin()
{
    int value;
    cout<<"Enter the value to be inserted: ";
    cin>>value;
    struct node *temp, *p;
    temp = create_node(value);
    if (start == NULL)
    {
        start = temp;
        start->next = NULL;        
    }
    else
    {
        p = start;
        start = temp;
        start->next = p;
    }
    cout<<"Element Inserted at beginning"<<endl;
}

/*
 * Inserting Node at last
 */
void single_llist::insert_last()
{
    int value;
    cout<<"Enter the value to be inserted: ";
    cin>>value;
    struct node *temp, *s;
    temp = create_node(value);
    s = start;
    while (s->next != NULL)
    {        
        s = s->next;      
    }
    temp->next = NULL;
    s->next = temp;
    cout<<"Element Inserted at last"<<endl;
}

/*
 * Insertion of node at a given position
 */
void single_llist::insert_pos()
{
    int value, pos, counter = 0;
    cout<<"Enter the value to be inserted: ";
    cin>>value;
    struct node *temp, *s, *ptr;
    temp = create_node(value);
    cout<<"Enter the postion at which node to be inserted: ";
    cin>>pos;
    int i;
    s = start;
    while (s != NULL)
    {
        s = s->next;
        counter++;
    }
    if (pos == 1)
    {
        if (start == NULL)
        {
            start = temp;
            start->next = NULL;
        }
        else
        {
            ptr = start;
            start = temp;
            start->next = ptr;
        }
    }
    else if (pos > 1  && pos <= counter)
    {
        s = start;
        for (i = 1; i < pos; i++)
        {
            ptr = s;
            s = s->next;
        }
        ptr->next = temp;
        temp->next = s;
    }
    else
    {
        cout<<"Positon out of range"<<endl;
    }
}

/* Delete element at a given position
 */
void single_llist::delete_pos()
{
    int pos, i, counter = 0;
    if (start == NULL)
    {
        cout<<"List is empty"<<endl;
        return;
    }
    cout<<"Enter the position of value to be deleted: ";
    cin>>pos;
    struct node *s, *ptr;
    s = start;
    if (pos == 1)
    {
        start = s->next;
    }
    else
    {
        while (s != NULL)
        {
            s = s->next;
            counter++;
        }
        if (pos > 0 && pos <= counter)
        {
            s = start;
            for (i = 1;i < pos;i++)
            {
                ptr = s;
                s = s->next;
            }
            ptr->next = s->next;
        }
        else
        {
            cout<<"Position out of range"<<endl;
        }
        free(s);
        cout<<"Element Deleted"<<endl;
    }
}

/*
 * Searching an element
 */
void single_llist::search()
{
    int value, pos = 0;
    bool flag = false;
    if (start == NULL)
    {
        cout<<"List is empty"<<endl;
        return;
    }
    cout<<"Enter the value to be searched: ";
    cin>>value;
    struct node *s;
    s = start;
    while (s != NULL)
    {
        pos++;
        if (s->info == value)
        {
            flag = true;
            cout<<"Element "<<value<<" is found at position "<<pos<<endl;
        }
        s = s->next;
    }
    if (!flag)
        cout<<"Element "<<value<<" not found in the list"<<endl;
}

/* Display Elements of a link list
 */
void single_llist::display()
{
    struct node *temp;
    if (start == NULL)
    {
        cout<<"The List is Empty"<<endl;
        return;
    }
    temp = start;
    cout<<"Elements of list are: "<<endl;
    while (temp != NULL)
    {
        cout<<temp->info<<"->";
        temp = temp->next;
    }
    cout<<"NULL"<<endl;
}

Double Linked List in c++ Program

/*
 * C++ Program to Implement Doubly Linked List
 */
#include<iostream>
#include<cstdio>
#include<cstdlib>
/*
 * Node Declaration
 */
using namespace std;
struct node
{
    int info;
    struct node *next;
    struct node *prev;
}*start;

/*
 Class Declaration
 */
class double_llist
{
    public:
        void create_list(int value);
        void add_begin(int value);
        void add_after(int value, int position);
        void delete_element(int value);
        void display_dlist();
        double_llist()
        {
            start = NULL;
        }
};

/*
 * Main: Conatins Menu
 */
int main()
{
    int choice, element, position;
    double_llist dl;
    while (1)
    {
        cout<<endl<<"----------------------------"<<endl;
        cout<<endl<<"Operations on Doubly linked list"<<endl;
        cout<<endl<<"----------------------------"<<endl;        
        cout<<"1.Create Node"<<endl;
        cout<<"2.Add at begining"<<endl;
        cout<<"3.Add after position"<<endl;
        cout<<"4.Delete"<<endl;
        cout<<"5.Display"<<endl;
        cout<<"6.Quit"<<endl;
        cout<<"Enter your choice : ";
        cin>>choice;
        switch ( choice )
        {
        case 1:
            cout<<"Enter the element: ";
            cin>>element;
            dl.create_list(element);
            cout<<endl;
            break;
        case 2:
            cout<<"Enter the element: ";
            cin>>element;
            dl.add_begin(element);
            cout<<endl;
            break;
        case 3:
            cout<<"Enter the element: ";
            cin>>element;
            cout<<"Insert Element after postion: ";
            cin>>position;
            dl.add_after(element, position);
            cout<<endl;
            break;
        case 4:
            if (start == NULL)
            {                    
                cout<<"List empty,nothing to delete"<<endl;  
                break;
            }
            cout<<"Enter the element for deletion: ";
            cin>>element;
            dl.delete_element(element);
            cout<<endl;
            break;
        case 5:
            dl.display_dlist();
            cout<<endl;
            break;
        case 6:
            exit(1);
        default:
            cout<<"Wrong choice"<<endl;
        }
    }
    return 0;
}

/*
 * Create Double Link List
 */
void double_llist::create_list(int value)
{
    struct node *s, *temp;
    temp = new(struct node);
    temp->info = value;
    temp->next = NULL;
    if (start == NULL)
    {
        temp->prev = NULL;
        start = temp;
    }
    else
    {
        s = start;
        while (s->next != NULL)
            s = s->next;
        s->next = temp;
        temp->prev = s;
    }
}

/*
 * Insertion at the beginning
 */
void double_llist::add_begin(int value)
{
    if (start == NULL)
    {
        cout<<"First Create the list."<<endl;
        return;
    }
    struct node *temp;
    temp = new(struct node);
    temp->prev = NULL;
    temp->info = value;
    temp->next = start;
    start->prev = temp;
    start = temp;
    cout<<"Element Inserted"<<endl;
}

/*
 * Insertion of element at a particular position
 */
void double_llist::add_after(int value, int pos)
{
    if (start == NULL)
    {
        cout<<"First Create the list."<<endl;
        return;
    }
    struct node *tmp, *q;
    int i;
    q = start;
    for (i = 0;i < pos - 1;i++)
    {
        q = q->next;
        if (q == NULL)
        {
            cout<<"There are less than ";
            cout<<pos<<" elements."<<endl;
            return;
        }
    }
    tmp = new(struct node);
    tmp->info = value;
    if (q->next == NULL)
    {
        q->next = tmp;
        tmp->next = NULL;
        tmp->prev = q;    
    }
    else
    {
        tmp->next = q->next;
        tmp->next->prev = tmp;
        q->next = tmp;
        tmp->prev = q;
    }
    cout<<"Element Inserted"<<endl;
}

/*
 * Deletion of element from the list
 */
void double_llist::delete_element(int value)
{
    struct node *tmp, *q;
     /*first element deletion*/
    if (start->info == value)
    {
        tmp = start;
        start = start->next;
        start->prev = NULL;
        cout<<"Element Deleted"<<endl;
        free(tmp);
        return;
    }
    q = start;
    while (q->next->next != NULL)
    {  
        /*Element deleted in between*/
        if (q->next->info == value)
        {
            tmp = q->next;
            q->next = tmp->next;
            tmp->next->prev = q;
            cout<<"Element Deleted"<<endl;
            free(tmp);
            return;
        }
        q = q->next;
    }
     /*last element deleted*/
    if (q->next->info == value)  
    {
        tmp = q->next;
        free(tmp);
        q->next = NULL;
        cout<<"Element Deleted"<<endl;
        return;
    }
    cout<<"Element "<<value<<" not found"<<endl;
}

/*
 * Display elements of Doubly Link List
 */
void double_llist::display_dlist()
{
    struct node *q;
    if (start == NULL)
    {
        cout<<"List empty,nothing to display"<<endl;
        return;
    }
    q = start;
    cout<<"The Doubly Link List is :"<<endl;
    while (q != NULL)
    {
        cout<<q->info<<" <-> ";
        q = q->next;
    }
    cout<<"NULL"<<endl;
}