int hasSolution(sudokuGrid game){
int solved;
cell candidateCell;
value trialValue;
if(isFull(game)){
solved = TRUE;
}else{
candidateCell = getEmptyCell(game);
trialValue = MIN_VALUE;
solved = FALSE;
while(!solved && (trialValue <= MAX_VALUE)){
if(isLegal(game, candidateCell, trialValue)){
setCell(game, candidateCell, trialValue);
if(hasSolution(game)){
solved = TRUE;
}else{
clearCell(game, candidateCell);
}
}
trialValue++;
}
}
return solved;
}
int solutionCount(sudokuGrid *game,int solutionsCuttoff) {
//this function destroys the board in the process of counting the number of solutions//
int position, trialValue, count;
//if the board is full up, we are done
if (isBoardFull(game)) {
count = 1;
} else {
count = 0;
position = getEmptyCell(game);
trialValue = MIN_VALUE;
while ((count < solutionsCuttoff) && (trialValue <= MAX_VALUE)) {
if (isLegalMove(game,position,trialValue)) {
commitMove(game,position,trialValue);
if (solutionCount(game,1)) {
//game with trial value in this position is solvable
count++;
}
//reset to a blank value to try another solution
commitMove(game,position,BLANK_VALUE);
}
trialValue++;
}
}
return count;
}
int isBoardFull(sudokuGrid *game) {
if (getEmptyCell(game) == -1) {
return TRUE;
} else {
return FALSE;
}
}
int hasSolution(sudokuGrid *game) {
int position, trialValue, solved;
//if the board is full, we are done
if (isBoardFull(game)) {
solved = TRUE;
} else {
solved = FALSE;
position = getEmptyCell(game);
trialValue = MIN_VALUE;
while (!solved && (trialValue <= MAX_VALUE)) {
if (isLegalMove(game,position,trialValue)) {
commitMove(game,position,trialValue);
if (hasSolution(game)) {
//game with trial value in this position is solvable
solved = TRUE;
} else {
//reset to a blank value to try another solution
commitMove(game,position,BLANK_VALUE);
}
}
trialValue++;
}
}
return solved;
}
int generateRandomBoard(sudokuGrid *game) {
int position, trialValue, solved;
int trialValues[NUM_VALUES];
int i,j;
//if the board is full, we are done
if (isBoardFull(game)) {
solved = TRUE;
} else {
//populate and then shuffle array of trial values
j = 0;
for (i = MIN_VALUE; i <= MAX_VALUE; i++) {
trialValues[j] = i;
j++;
}
shuffleArr(trialValues,NUM_VALUES);
solved = FALSE;
position = getEmptyCell(game);
j = 0;
while (!solved && (j < NUM_VALUES)) {
trialValue = trialValues[j];
if (isLegalMove(game,position,trialValue)) {
commitMove(game,position,trialValue);
if (generateRandomBoard(game)) {
//game with trial value in this position is solvable
solved = TRUE;
} else {
//reset to a blank value to try another solution
commitMove(game,position,BLANK_VALUE);
}
}
j++;
}
}
return solved;
}
