public ArrayList<String> solve() {
// save base/original puzzle
savePuzzle(0, 0);
Boolean succeeded = false;
outerloop:
for (int i = 0; i < 81; i++) { // for each cell in the puzzle
if (cells.get(i).getPossibilities().length() > 1) {
succeeded = false;
while (trialPos < cells.get(i).getPossibilities().length()) {
String trialValue = String.valueOf(cells.get(i).getPossibilities().charAt(trialPos));
try {
add(trialValue, i);
if (solved()) {
break outerloop;
} else { // Value was successfully added (didn't break try)
succeeded = true;
// System.out.println("Succeeded with " + trialValue + " at cell " + i + " trialPos =
// " + trialPos);
savePuzzle(i, trialPos + 1);
trialPos = 0;
break;
}
} catch (Exception e) {
// Value was NOT successfully added. Reset puzzle and try next value.
// System.out.println("Failed with " + trialValue + " at cell " + i + " trialPos = " +
// trialPos);
resetPuzzle();
}
trialPos++;
}
} else if (cells.get(i).getPossibilities().length() == 1) {
succeeded = true;
// System.out.println("One possible value at cell " + i);
trialPos = 0;
}
if (succeeded == false) {
// no value worked. Backtrack.
// System.out.println("*****FAILED, GO BACK*****");
i = goBack();
}
}
ArrayList<String> result = new ArrayList<>();
for (Cell c : cells) {
result.add(c.getPossibilities());
}
return result;
}
public void add(String value, int pos) throws Exception {
Cell tempCell = cells.get(pos);
tempCell.add(value);
cells.set(pos, tempCell);
// and eliminate that value from possibilities of relevant cells
for (int i = 0; i < 81; i++) {
if (areRelevant(i, pos)) {
tempCell = cells.get(i);
int beforeLength = tempCell.getPossibilities().length();
tempCell.eliminate(value);
if (beforeLength > 1 && tempCell.getPossibilities().length() == 1) {
add(tempCell.getPossibilities(), i);
}
cells.set(i, tempCell);
}
}
}