Eigen sparse 基本操作：构造 & 输出

#include 
#include "Eigen/Sparse"
int main()
{
	Eigen::SparseMatrix m(3, 3);
	std::vector > triple;
	for (int i = 0; i < 3; i++) {
		for (int j = 0; j < 3; j++) {
			triple.push_back(Eigen::Triplet(i, j, 0.1));
		}
	}
	triple.push_back(Eigen::Triplet(1, 1, 0.1));相同下标重复插入，则表示相加
	m.setFromTriplets(triple.begin(), triple.end());
	//std::cout << m << std::endl; //直接这样输出也是可以的
	for (int k = 0; k < m.outerSize(); ++k) {
		for (Eigen::SparseMatrix::InnerIterator it(m, k); it; ++it)
		{
			//std::cout << it.row() << " " << it.col() << " : " << it.value() << std::endl;
			std::cout << it.value() << " ";
		}
		std::cout << std::endl;
	}
	return 0;
}