Linear Programming, Kakuro Puzzles, Gurobi, Puzzle Game, Discrete Optimization.
Constraint (2) We want the numbers placed in the empty cells of a horizontal run to sum up to the horizontal clue. The term in this nested summation is x_{i,j,k} · k. Again, x_{i,j,k} is only 1 if we place the value k in the cell (i,j), otherwise x_{i,j,k} is 0. By definition of our binary