Linear Programming, Kakuro Puzzles, Gurobi, Puzzle Game, Discrete Optimization.
variable x_{i,j,k}. The i and j values represent the coordinates of the empty space and k is an integer in the set {1, 2, 3, 4, 5, 6, 7, 8, 9}. Since x_{i,j,k} is a binary variable, x_{i,j,k} ∈ {0, 1}. If x_{i,j,k} = 1, then the empty space corresponding to coordinates (i, j) = k. In other words,