"""

 Name:

 Author: Eugen Sawin <sawine@informatik.uni-freiburg.de>

 """

 def main():    

     goal = ((0, 0, 0), (3, 3, 1))

     node = Node(((3, 3, 1), (0, 0, 0)))

     frontier = [node]

     explored = set()

     solutions = set()

     while len(frontier):

         node = frontier.pop()

         explored.add(node.state)      

         for action in actions(node.state):            

             child = Node(apply(node.state, action), node, action)      

             if child.state == child.parent.state:

                 print child

                 return

             if child.state not in explored and child not in frontier:

                 if child.state == goal:

                     solutions.add(child)

                 else:

                     frontier.append(child) 

     for i, s in enumerate(solutions):

         print "solution ", i

         parent = s.parent

         parents = []

         while parent:

             parents.append(parent)            

             parent = parent.parent

         print [p.state for p in reversed(parents)]

 def negate(action):

     return (-action[0], -action[1], -action[2]) 

 def apply(state, action):

     if len(state) == 2:

         return (apply(state[0], action), apply(state[1], negate(action)))

     return (state[0] + action[0], state[1] + action[1], state[2] + action[2])

 def actions(state):      

     actions = [(-2, 0, -1), (-1, 0, -1), (-1, -1, -1), (0, -2, -1), (0, -1, -1)]

     actions.extend([negate(a)for a in actions])

     states = [apply(state, a) for a in actions]   

     good_states = [s[0] for s in states if s[0][2] >= 0 and s[1][2] >= 0 

                    and (s[0][0] >= s[0][1] or not s[0][0]) 

                    and (s[1][0] >= s[1][1] or not s[1][0])

                    and s[0][1] >= 0 and s[1][1] >= 0

                    and s[0][2] >= 0 and s[1][2] >= 0]

     return [a for a in actions if apply(state[0], a) in good_states]

 class Node(object):

     def __init__(self, state, parent=None, action=None, cost=None):

         self.state = state

         self.parent = parent

         self.action = action

         self.cost = cost

 from argparse import ArgumentParser

 def parse_arguments():

     parser = ArgumentParser(description="Parses simple modal logic syntax.")

     parser.add_argument("-f", "--formula", help="your formula") 

     return parser.parse_args()

 if __name__ == "__main__":

     main()