Solution (source code)

= Solution

Since every <eigenvalue> is nonzero, $S$ is an <invertible matrix>. Multiplying $S\mathbf u_i=\lambda_i\mathbf u_i$ by the <inverse matrix> gives
$$
\boxed{S^{-1}\mathbf u_i=\lambda_i^{-1}\mathbf u_i}.
$$
Hence the <eigenvectors> are unchanged and the corresponding <eigenvalues> are $1/\lambda_i$.