规范模块目录和第三方依赖结构

third_party/eigen3/doc/examples/TutorialLinAlgInverseDeterminant.cpp

@@ -0,0 +1,16 @@
+#include <iostream>
+#include <Eigen/Dense>
+
+using namespace std;
+using namespace Eigen;
+
+int main()
+{
+   Matrix3f A;
+   A << 1, 2, 1,
+        2, 1, 0,
+        -1, 1, 2;
+   cout << "Here is the matrix A:\n" << A << endl;
+   cout << "The determinant of A is " << A.determinant() << endl;
+   cout << "The inverse of A is:\n" << A.inverse() << endl;
+}