An Optimal Mastermind (4,7) Strategy and More Results in the Expected Case

Abstract

This paper presents an optimal strategy for solving the 4 peg-7 color Mastermind MM(4,7) in the expected case (4.676) along with optimal strategies or upper bounds for other values. The program developed is using a depth-first branch and bound algorithm relying on tight upper bound, dynamic lower bound evaluation and guess equivalence to prune symmetric tree branches.