#include <cassert>
#include <cstddef>
#include <iterator>
#include <list>
#include <vector>

template <typename T>
auto count_bytes(T const& data);

namespace details
{
    
    template <typename Container>
    auto count_bytes(Container const& container, int)
	-> decltype(std::begin(container), std::size_t{})
    {
	std::size_t count = 0;
	for (auto const& element : container)
	{
	    count += ::count_bytes(element);
	}
	return count;
    }
        
    template <typename T>
    auto count_bytes(T const& data, float)
    {
	return sizeof(data);
    }
    
}

template <typename T>
auto count_bytes(T const& data)
{
    return details::count_bytes(data, 0);
}

int main()
{
    int x { 9 };
    assert(count_bytes(x) == sizeof(int));

    std::vector<int> v { 1, 2, 3 };
    assert(count_bytes(v) == 3 * sizeof(int));

    std::list<std::vector<std::string>> l {
	{ "a", "bc" }, // 3 chars
	{ },           // 0 chars
	{ "defg" },    // 4 chars
    };

    // 3 + 0 + 4 = 7 chars
    assert(count_bytes(l) == 7 * sizeof(char));

    std::vector<int> array[] = {
	{ 1, 2, 3, 4 }, // 4 ints
	{ 5, 6 },       // 2 ints
	{ },            // 0 ints
	{ 7, 8 },       // 2 ints
    };

    // 4 + 2 + 0 + 2 = 8 ints
    assert(count_bytes(array) == 8 * sizeof(int));
}