A C++ program to use inputs from a file to perform basic operations on a Linked List

inputs.txt

This file contains the input for the program link_list_using_file.cpp. Change the content in this file to change the inputs.

link_list_using_files.cpp

#include<iostream>
#include<fstream>
using namespace std;
class single_llist
{
	struct node
	{
		char info;
		struct node *next;
	}*start;

	public:
		single_llist() 
		{
	                start = NULL;
		}
		
		node *create_node(char data)
		{
			struct node *temp, *s;
			temp = new(struct node); 
			if (temp == NULL)
			{
				cout<<"Memory not allocated "<<endl;
				return NULL;
			}
			else
			{
				temp->info = data;
				temp->next = NULL;     
		        	return temp;
			}
		}
		
		void insert_begin(char data)
		{
			struct node *temp, *p;
			temp = create_node(data);
			if (start == NULL)
			{
				start = temp;
				start->next = NULL;    
			} 
			else
			{
				p = start;
				start = temp;
				start->next = p;
			}
			cout<<"Element Inserted at beginning"<<endl;
		}
		
		void insert_last(char data)
		{
			struct node *temp, *s;
			temp = create_node(data);
			s = start;
			while (s->next != NULL)
				s=s->next;  
			temp->next = NULL;
			s->next = temp;
			cout<<"Element Inserted at last"<<endl;  
		}
		     
		void insert_pos(char data)
		{
			int pos, counter = 0; 
			struct node *temp, *s, *ptr;
			temp = create_node(data);
			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;
			}
		}		
    		
     		

		void delete_pos()
		{		
			int pos, i, counter = 0;
			if (start == NULL)
			{
				cout<<"List is empty"<<endl;
				return;
			}
			cout<<"Enter the position of data 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;
				}
				delete s;
				cout<<"Element Deleted"<<endl;
			}
		}
		     
		void update(char data)
		{
			int pos, i;
			if (start == NULL)
			{
				cout<<"List is empty"<<endl;
				return;
			}
			cout<<"Enter the node postion to be updated: ";
			cin>>pos;
			struct node *s, *ptr;
			s = start;
			if (pos == 1)
			{
				start->info = data; 
			}
			else
			{
				for (i = 0;i < pos - 1;i++)
				{
					if (s == NULL)
					{
						cout<<"There are less than "<<pos<<" elements";
						return;
					}
					s = s->next;
				}
				s->info = data;  
			}
			cout<<"Node Updated"<<endl;
		} 
		    
		void search(char data)
		{
			int pos = 0;
			bool flag = false;
			if (start == NULL)
			{
				cout<<"List is empty"<<endl;
				return;
			}
			struct node *s;
			s = start;
			while (s != NULL)
			{
				pos++;
				if (s->info == data)
				{
					flag = true;
					cout<<"Element "<<data<<" is found at position "<<pos<<endl;
				}
				s = s->next;
			}
			if (!flag)
			cout<<"Element "<<data<<" not found in the list"<<endl;  
		}
		  
		void 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;
		}
};

int main()
{
	fstream inputs;
	inputs.open("inputs.txt",ios::in);
	char data;
	int choice, nodes, element, position, i;
        single_llist sl;
        do
        {
		cout<<"\nMenu\n1.Insert at Begining\n2.Insert at Last\n3.Insert at position\n4.Delete\n5.Update\n6.Search\n7.Display\n8.Exit\nEnter Choice: ";
		cin>>choice;	
		switch(choice)
		{
			case 1:	if(inputs>>data)
					sl.insert_begin(data);
				else
					cout<<"\nFile Error";
				break;
			case 2:	if(inputs>>data)
					sl.insert_last(data);
				else
					cout<<"\nFile Error!!";
				break;
			case 3:	if(inputs>>data)
					sl.insert_pos(data);
				else
					cout<<"\nFile Error!!!";
				break;
			case 4:	sl.delete_pos();
				break;
			case 5:	if(inputs>>data)
					sl.update(data);
				else
					cout<<"\nFile Error!!";
				break;
			case 6:	cout<<"\nEnter element to be searched: ";
				cin>>data;
				sl.search(data);
				break;
			case 7:	sl.display();
				break;
			case 8:	break;
			default:cout<<"Wrong choice"<<endl;
		}
	}while((choice!=8)&&(!inputs.eof()));
	cout<<"\n\n";
	return 0;
}