def solveProblem(self, problem: Sudoku):
# Fill in all the possible tiles with educated predictions.
while True:
if self.applyNakedSingle(problem):
continue
if self.applyNakedTuple(problem):
continue
break
# Check if we find the solution after applying Sudoku.
if self.goalTest(problem):
return problem
# Save updated state of the problem before making guesses with candidates.
beforeUpdateProblem = copy.deepcopy(problem)
# Backtrack from populated sudoku problem
tile = self.findMostConstrainedTile(problem)
for index in range(len(tile.candidates)):
if not problem.isConflicting(tile.candidates[index],
rowIndex=tile.rowIndex,
colIndex=tile.colIndex):
problem.assignValue(value=tile.candidates[index],
row=tile.rowIndex,
col=tile.colIndex)
updatedProblem = self.solveProblem(problem)
if self.goalTest(updatedProblem):
return updatedProblem
else:
problem = beforeUpdateProblem
tile = problem.state[tile.rowIndex][tile.colIndex]
# No candidates, Hit dead end
return None
