Similar matrices

Algebra Level 2

Which of these matrices is not similar to any of the other three?

Notation: Two square matrices $A,B$ with complex entries are similar if and only if there is an invertible square matrix $P$ such that $A = PBP^{-1}.$

\begin{pmatrix} 1&1&1\\0&1&1\\0&0&1 \end{pmatrix}

\begin{pmatrix} 1&0&1\\0&1&1\\0&0&1 \end{pmatrix}

\begin{pmatrix} 1&1&1\\0&1&0\\0&0&1 \end{pmatrix}

\begin{pmatrix} 1&0&1\\0&1&0\\0&0&1 \end{pmatrix}