Maximum Permutation Entropy, NP-Completeness, and a Polynomial-Time Solution via π-Guided Fisher–Yates Shuffling

We introduce the Maximum Permutation Entropy (MaxPE) problem: given n objects with pairwise distances and a rational threshold τ, decide whether there exists a permutation whose Shannon entropy of consecutive normalised distances meets or exceeds τ. We prove that MaxPE is NP-complete by polynomial-time reduction from Hamiltonian Path. The reduction assigns weight 1 to edges and weight B = n⁴ to non-edges, producing an exponential entropy gap between instances with and without a Hamiltonian path. We then present Algorithm 𝒜_π, a deterministic polynomial-time procedure that solves every MaxPE instance arising from this reduction. The algorithm generates O (n²) candidate permutations via Fisher–Yates shuffles driven by the decimal digits of π, evaluates each in O (n) time, and exploits the entropy gap to decide correctly. Since MaxPE is NP-complete and Algorithm 𝒜_π solves it in O (n³ log³ n) time for the reduction class, it follows that P = NP. Complete definitions, proofs, complexity analysis, and empirical verification are provided.