List

[thanhquan1704]

#include <iostream>
#include <list>
using namespace std;
template <typename T>
class Set {
private:
	list<int> storage;
public:
	size_t size() const { return storage.size(); }
	void insert(const T&);
};
template <typename T>
void Set<T>::insert(const T& x)
{
	for (auto i : storage)
		if (i == x)
			return;
	storage.insert(storage.begin(), x);
}
int main()
{
	Set<int> nums;
	nums.insert(3);
	nums.insert(3);
	nums.insert(5);
	for (int i = 0; i < nums.size(); i++)
		cout << nums[i];
	system("pause");
}

I want to show all elements of nums, but my code is wrong. Can anybody help please?

[Peter87]

If you want be able to access element like that you need to overload the subscript operator.

int operator[](std::size_t index) const;

[nuderobmonkey]

Imho a list provides no subscript operator, and implementing such would be very slow at execution time.

#include <iostream>
#include <list>
using namespace std;
template <typename T>
class Set {
private:
	list<T> storage;
	typename list<T>::iterator itr;

public:
	Set() : itr{ storage.begin() } {}  // the construtor
	size_t size() const { return storage.size(); }
	void insert(const T&);

	auto begin() { return storage.begin(); }
	auto end() { return storage.end(); }

	// operator overloads
	auto & operator*() { return *itr; }
	auto const & operator*() const { return *itr; }
	auto & operator++() { return ++itr; } //prefix
	auto & operator++(int) { auto tmp = itr; ++itr; return tmp; } //postfix
};
template <typename T>
void Set<T>::insert(const T& x)
{
	for (auto i : storage)
		if (i == x)
			return;
	storage.insert(storage.begin(), x);
}
int main()
{
	Set<int> nums;
	nums.insert(3);
	nums.insert(3);
	nums.insert(5);
	for (auto & n : nums)
		cout << n;

    // the above is 'syntactic sugar' for:
	for( auto itr = nums.begin(); itr != nums.end(); ++itr)
	    cout << *itr;
}

*edited

[Peter87]

If you need fast random-access you could use std::vector instead of std::list which is probably a better choice anyway.