The numerical complexity of a symmetric tridiagonal matrix for the solution of eigenvalue comes out o(n^2).
https://eigen.tuxfamily.org/dox/classEigen_1_1SelfAdjointEigenSolver.html#adf397f6bce9f93c4b0139a47e261fc24,
If we use the same code, and calculate the both the eigenvalues and eigenvectors of the matrix, then the complexity is o(n^3).
why it change so much.?