Vector of Vectors vs List of Vectors

vov_vs_lov.cpp

// Vector of vectors
{
	// Initialize vector of vectors
	std::vector<std::vector<int>> vov;
	vov.resize(1);
	vov.back() = { 1, 2, 3, 4 };

	// Get reference to first list - used as argument for the threads
	auto& ref = vov.back();

	// Add a load of containers to make it reallocate
	for (int i = 0; i < 200; i++)
		vov.push_back(std::vector<int>{ i, i + 1, i + 2, 1000 });

	// Error! `ref` is invalid - the container has been moved
	printf("ref = { %d, %d, %d, %d }\n", ref[0], ref[1], ref[2], ref[3]);
}

// List of vectors
{
	// Initialize list of vectors
	std::list<std::vector<int>> lov;
	lov.resize(1);
	lov.back() = { 1, 2, 3, 4 };

	// Get reference to first list - used as argument for the threads
	auto& ref = lov.back();

	// Add a load of containers to make it reallocate
	for (int i = 0; i < 200; i++)
		lov.push_back(std::vector<int>{ i, i + 1, i + 2, 1000 });

	// Everything is fine, ref is still refering to the same container which has not been moved
	printf("ref = { %d, %d, %d, %d }\n", ref[0], ref[1], ref[2], ref[3]);
}