C program help with sudoku puzzle routine to solve?

[anish_ab]

We are one routine short of solving the Sudoku. That routine is a recursive routine called ProcessCell. Here is the pseudocode for ProcessCell, implement it in C:

/* Add these definitions to the top of your source module */
#define FIRSTATTEMPT(1)
#define LASTATTEMPT(9)

ProcessCell (CELL aCells[][SUDOKULIMIT], int nRow, int nCol)
{
Set nOrgCell flag to indicate if this cell was set in the puzzle definition (aCell[nRow][nCol].m_nOrgVal != 0)

Define and initialize nLastCell flag to FALSE

Print a message indicating the row and column we are processing. Start the message with \r so we stay on the same line

if GetNextCell(nRow, nCol, &nNextRow, &nNextCol) returns FALSE then
nLastCell = TRUE

if this an original cell (nOrgCell != FALSE), then
if this is the last cell (nLastCell != FALSE) then
return TRUE
else
return the result of a recusive call to ProcessCell with the next
row and next column

/* At this point we know it's not an original cell (i.e. not in the puzzle definition) */

set nAttempt to FIRSTATTEMPT
Loop while nAttempt <= LASTATTEMPT
{
if nAttempt is in current row, column, or subgrid (use Check...) then
continue;

/* The current value of nAttempt is ok for this cell for now */
put nAttempt in the current value for this cell

if this is the last cell then
return TRUE -- we solved the puzzle!!

Call ProcessCell recursively with nNextRow and nNextCol
if the recursive ProcessCell call returns TRUE then
return TRUE -- we solved the puzzle!!

/* other wise we'll continue with the next value for nAttempt */
Your loop should increment nAttempt each time through
}// End of nAttempt loop

/* If we exit the loop then no number from FIRSTATTEMPT to
* LASTATTEMPT worked for this cell. */
Set current value for cell back to 0.

/* Tell the caller that a cell prior to this one must change */
return FALSE -- we're not able to solve the puzzle with the values
that are currently in the previous cells
} // end of ProcessCell

To solve the puzzle you must start with a call to ProcessCell in main for the first cell in row-wise order:

void main()
{
Declare and initialize stuff

LoadArray
PrintArray
nResult = ProcessCell(aCells, 0, 0)

if (nResult)
{
PrintArray
}
else
{
Print an "unsolvable" message
}
}