Puzzle—Integer Linear Programming: Spreadsheet Solver Excellence Without Excel

Abstract

Because of the limitations on problem size with the built-in optimization solver in Microsoft Excel, other software applications are required to illustrate the power of integer linear programming in spreadsheets. The built-in linear optimization solver in LibreOffice Calc allows much larger problems. In this paper, we build a spreadsheet in LibreOffice Calc to solve sudoku problems and a simple generalization that further illustrates the power of integer linear programming in spreadsheets. The generalization we consider, n-doku, also introduces an interesting puzzle that includes, as a special case, a union of multiple sudoku puzzles. Besides further demonstrating the power of integer linear programming in spreadsheets, we use the n-doku solutions to develop optimization intuition and to, more generally, foster critical thinking. We use this spreadsheet in the classroom to transition from continuous to categorical decisions, emphasizing the idea of one-hot encoding. We also illustrate multiple optima and add preferences to sudoku puzzles as a way introduce multiobjective optimization. Supplemental Material: The online supplement is available at https://doi.org/10.1287/ited.2022.0068 .