Accessing any element on a list stl c++

[kramsuiluj]

How do i access a part of the list if there's no initial value ?

This is the program I'm working with:

#include <iostream>
#include <string>
#include <list>
using namespace std;

int main ()
{
	
	string item, desc, remove;
	int num, qty;
	list <string> items;
	list <string> description;
	list <int> quantity;
	list <string> :: iterator it1 = items.begin();
	list <string> :: iterator it2 = description.begin();
	list <int> :: iterator it3 = quantity.begin();
	list <string> :: iterator show;
	list <int> :: iterator showInt;
	
	main:
	system("cls");
	cout << "Inventory Management System\n\n";
	cout << "[0]Exit\n";
	cout << "[1]Add Item\n";
	cout << "[2]Remove Item\n";
	cout << "[3]View an Item\n";
	cout << "[4]View All\n\n";
	cout << "Input: ";
	cin >> num;
	
	switch (num)
	{
		case 0:
			system("cls");
			return 0;
			break;
			
		case 1:
			system("cls");
			cout << "Enter the Item Name: ";
			cin >> item;
			items.push_front(item);
			cout << "Enter the Item Description: ";
			cin >> desc;
			description.push_front(desc);
			cout << "Enter the Item Quantity: ";
			cin >> qty;
			quantity.push_front(qty);
			cout << "\nItem has been added successfully.\n";
			system("pause");
			goto main;
			break;
			
		case 2:
			system("cls");
			cout << "Enter the name of the item you want to remove: ";
			cin >> remove;
			items.remove(remove);
			cout << endl;
			system("pause");
			goto main;
			break;
			
		case 3:
			system("cls");
			cout << "Enter the name of the Item you want to view: ";
		
		case 4:
			system("cls");
			cout << "List of Items\n\n";
			for (show = items.begin(); show != items.end(); show++) {
				cout << "\t" << "Item Name: " << *show << endl;
			}
			cout << endl;
			system("pause");
			goto main;
	}
	
}

[MikeyBoy]

How do i access a part of the list if there's no initial value ?

What do you mean? If there's nothing in the list, there's nothing to access.

If the list is empty, items.begin() == items.end().

BTW, trying to maintain multiple parallel lists seems like an error-prone headache. Why not have a single list of structs?

[kramsuiluj]

Ah, lets say i ran the program and i have 3 or more element in the list.
Uhm, is it possible to organize the output using a single list ?

[Repeater]

What does "organise the output" mean?

[Handy Andy]

Hello kramsuiluj,

Yes it could be done, but it is more work than you need.

"goto" statements are nice, but should be avoided. They can be replaced with a while or do/while loop.

This is one possible solution.

#include <iostream>
#include <limits>  // <--- Added.
#include <string>
#include <list>

using namespace std;

struct Items
{
	Items(std::string itemName, std::string itemDes, int quantity)
	{
		s_itemName = itemName;
		s_itemDes = itemDes;
		s_quantity = quantity;
	}

	std::string s_itemName;
	std::string s_itemDes;
	int s_quantity{};
};

int main()
{
	bool cont{ true };  // <--- Added.
	string item, desc, remove;
	int num, qty;
	list<Items> items; // <--- list of structs.

	// <--- Not worked on these yet.
	//list <string> items;
	//list <string> description;
	//list <int> quantity;
	//list <string> ::iterator it1 = items.begin();
	//list <string> ::iterator it2 = description.begin();
	//list <int> ::iterator it3 = quantity.begin();
	//list <string> ::iterator show;
	//list <int> ::iterator showInt;

//main:

	do
	{
		system("cls");
		cout << "Inventory Management System\n\n";
		cout << "[0]Exit\n";
		cout << "[1]Add Item\n";
		cout << "[2]Remove Item\n";
		cout << "[3]View an Item\n";
		cout << "[4]View All\n\n";
		cout << "Input: ";
		cin >> num;

		switch (num)
		{
			case 0:  // <--- Changed.
				system("cls");
				cont = false;  // <--- Changed. Added.
				break;

			case 1:
				system("cls");
				cout << "Enter the Item Name: ";
				std::getline(std::cin, item);
				//items.push_front(item);
				cout << "Enter the Item Description: ";
				std::getline(std::cin, desc);
				//description.push_front(desc);
				cout << "Enter the Item Quantity: ";
				cin >> qty;
				std::cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');  // <--- Requires header file <limits>. Clears the input buffer before next "std::getline".
				//quantity.push_front(qty);
				items.emplace_front(item, desc, qty);
				cout << "\nItem has been added successfully.\n\n\n";
				system("pause");
				//goto main;
				break;

			case 2:
				system("cls");
				cout << "Enter the name of the item you want to remove: ";
				cin >> remove;
				//items.remove(remove);
				cout << endl;
				system("pause");
				//goto main;
				break;

			case 3:
				system("cls");
				cout << "Enter the name of the Item you want to view: ";

			case 4:
				system("cls");
				cout << "List of Items\n\n";
				//for (show = items.begin(); show != items.end(); show++) {
				//	cout << "\t" << "Item Name: " << *show << endl;
				//}
				cout << endl;
				system("pause");
				//goto main;
		}  //End switch.
	} while (cont);

	return 0;  // <--- Not required, but makes a good break point.
}

In case 0 the "return" statement is the wrong place to end the program, although it will work. Also because of the "return" the "break" statement is never reached.

In case 1 the use of "std::getline" is a better choice as formatted input of cin >> item; will stop at the first white space leaving whatever is left in the input buffer for the next "std::cin", So, in "Item 1" "item" will be put into the variable "item" leaving the "1" in the input buffer for cin >> desc; to extract.

For now this is as far as I have progressed. First I like to get the code that populates the list, or whatever it may be, working so that I have something to work with for the rest of the program.

Hope that helps,

Andy