In this paper we show that the Mastermind Satisfiability Problem (MSP) is NPcomplete. Mastermind is a popular game which can be turned into a logical puzzle called the Mastermind Satisfiability Problem in a similar spirit to the Minesweeper puzzle [5]. By proving that MSP is NP-complete, we reveal its intrinsic computational property that makes it challenging and interesting. This serves as an ...

SUMMARY BlockSum, also known as KeisanBlock in Japanese, is a Latin square filling type puzzle, such as Sudoku. In this paper, we prove that the decision problem whether a given instance of BlockSum has a solution or not is NP-complete.