  The core entropy of polynomials, recently introduced by W. Thurston, is a
dy-namical invariant extending topological entropy for real maps to complex
polynomials, whence providing a new tool to study the parameter space of
polynomials. The base is a combinatorial algorithm allowing for the computation
of the core entropy given by Thurston, but without supplying a proof. In this
paper, we will describe his algorithm and prove its validity.
