a field called grid that refers to a two$-$dimensional array of integers. This array will be used to store the current contents of the puzzle, such that grid$[$r$][$c$]$ stores the current value in the cell at row r$,$ column c of the puzzle. A value of $0$ is used to indicate a blank cell.a field called valIsFixed that refers to a two$-$dimensional array of booleans. It is used to record whether the value in a given cell is fixed $($i$.$e$.,$ part of the original puzzle$).$ valIsFixed$[$r$][$c$]$ is true if the value in the cell at row r$,$ column c is fixed, and false otherwise. For example, in the original puzzle above, there is a fixed $4$ in the cell at row $0,$ column $1($the second cell in the top row$),$ and thus valIsFixed$[0][1]$ would be true for that puzzle.