class Solver(ABC):
def __init__(self, sequence):
self.sequence = sequence # The sequence of the colors
self.faces = Faces() # Datastructure to model the color constraint
self.partial = dict() # Contains the partial solutions
self.solutions = 0
self.steps = 0
@property
@abstractmethod
def starting_points():
pass
def solve(self):
""" Start solving from every start point """
for coord in self.starting_points:
self._solve(coord, 0)
return self.solutions, self.steps
def _solve(self, coordinate, depth):
""" Recursive step """
# Condition for termination: The cube is completed
if depth == len(self.sequence) - 1:
self.solution()
return True
self.steps += 1
color = self.sequence[depth]
if self.constraints(coordinate, color):
self.push(coordinate, color, depth)
# Recursively solve for every neighbor
for neighbor in neighbors(coordinate):
if neighbor not in self.partial: # Only use free spaces
self._solve(neighbor, depth + 1)
self.pop(coordinate, color)
def push(self, coordinate, color, depth):
""" Step in: Go forward in the sequence and add the step to partial solution """
self.partial[coordinate] = (color, depth)
self.faces.push(coordinate, color)
def pop(self, coordinate, color):
""" Step out: Go backwards in the sequence and remove the step from the partial solution """
self.faces.pop(coordinate, color)
del self.partial[coordinate]
def solution(self):
""" Is called when a solution is found """
self.solutions += 1
human(self.partial)
@abstractmethod
def constraints(self, coordinate, color):
""" Run checks to limit the recursion """
return True
