Exemplo n.º 1
0
    def singleSourceShortestPath(self, srcID):
        assert (srcID >= 0 and srcID < self.n)
        # Implement Dijkstra's algorithm
        # Input:
        # self --> a reference to a MyGraph instance
        # srcID: the id of the source vertex.
        # Expected Output: (d,pi)
        #    d  --> Map each vertex id v to the distance from srcID
        #    pi --> Map each reachable vertex id v (except for srcID) to a parent.

        # Initialize the priority queue
        pq = PriorityQueue(self.n) #create the priority queue

        for i in range(0,self.n): # Iterate through all vertex ID
            if ( i == srcID):     # If ID is srcID
                pq.set(i,0.0)     # Distance of srcID should be zero
            else:                 # ID is not srcID
                pq.set(i, pq.Inf) # Distance should be infinity

        d = {}  # Initialize the map with distances to nodes
        pi = {} # Initialize the map with parents of vertices

        d[srcID] = 0 # first node to dist map since while won't catch it.

        while not pq.isEmpty():
            min = pq.extractMin()
            # Look at neighbors
            for neighbor in self.adjList[min[0]]: # where neighbor has not yet been removed from pq?
                alt = min[1] + neighbor[1]
                if pq.hasKey(neighbor[0]) and alt < pq.get(neighbor[0]): # previously stored needs to be replayed
                    # Update distances and parents everywhere
                    pq.set(neighbor[0], alt)
                    d[neighbor[0]] = alt
                    pi[neighbor[0]] = min[0]
        return (d,pi)
Exemplo n.º 2
0
    def singleSourceShortestPath(self, srcID):
        assert (srcID >= 0 and srcID < self.n) # ensure that srcID is between 0 and size of graph.
        # Implement Dijkstra's algorithm
        # Input:
        # self --> a reference to a MyGraph instance
        # srcID: the id of the source vertex.
        # Expected Output: (d,pi)
        #    d  --> Map each vertex id v to the distance from srcID
        #    pi --> Map each reachable vertex id v (except for srcID) to a parent.

        # Initialize the priority queue
        pq = PriorityQueue(self.n) #create the priority queue
        
        for i in range(0,self.n): # Iterate through all vertex ID
            if  i == srcID:     # If ID is srcID
                pq.set(i, 0.0)     # Distance of srcID should be zero
            else:                 # ID is not srcID
                pq.set(i, pq.Inf) # Distance should be infinity
        
        d = {}  # Initialize the map with distances to nodes
        pi = {} # Initialize the map with parents of vertices

        while not pq.isEmpty():  # loop until priority queue is empty.
            (node, dist) = pq.extractMin() # extract smallest dist node.
            d[node] = dist # update dictionary with shortest distance.
            for (vertex, weight) in self.adjList[node]: # check the adjacency list of popped node.
                newDist = dist + weight # calculate new distance.
                if pq.hasKey(vertex): # if we haven't already popped the node in the adjacency list yet.
                    if newDist < pq.get(vertex): # check distance vs new calculated dist.
                        pq.set(vertex, newDist) # update priority queue.
                        pi[vertex] = node # update parent list.

        return (d, pi)
Exemplo n.º 3
0
    def singleSourceShortestPath(self, srcID):
        assert (srcID >= 0 and srcID < self.n)

        # Implement Dijkstra's algorithm
        # Input:
        # self --> a reference to a MyGraph instance
        # srcID: the id of the source vertex.
        # Expected Output: (d,pi)
        #    d  --> Map each vertex id v to the distance from srcID
        #    pi --> Map each reachable vertex id v (except for srcID) to a parent.

        # Initialize the priority queue
        pq = PriorityQueue(self.n)  #create the priority queue
        cur = self
        for i in range(0, self.n):  # Iterate through all vertex ID
            if (i == srcID):  # If ID is srcID
                pq.set(i, 0.0)  # Distance of srcID should be zero
            else:  # ID is not srcID
                pq.set(i, pq.Inf)  # Distance should be infinity

        d = {}  # Initialize the map with distances to nodes
        pi = {}  # Initialize the map with parents of vertices

        minKey, minDist = pq.extractMin()

        d[minKey] = minDist  #set orignal source distance to 0
        pi[minKey] = minKey  #set sources to orginal source

        while (pq.isEmpty() == False):  # COMPLETE the Dijkstra code here

            lst = self.adjList[
                minKey]  #grap array of lists of format (vertices,weight) for node minKey
            for n in lst:  #loop through said list

                ##grap the next node attached to this node somehow
                dist = n[1] + minDist  #grab distance from list

                node = n[0]  #grab node from list
                if (pq.hasKey(node)
                    ):  #check if that nodes min dist has been found
                    if (
                            pq.get(node) > dist
                    ):  #check if path to the node from minKey is less then current path
                        pq.set(node,
                               dist)  #set the nodes distance in the queue
                        d[node] = dist  #set the nodes distance in the return array
                        pi[node] = minKey  #sets the nodes parents

            minKey, minDist = pq.extractMin(
            )  #extract next node dont need to extract last node as all the paths will be filled would probably work better in a do while loop

        return (d, pi)
Exemplo n.º 4
0
    def singleSourceShortestPath(self, srcID):
        assert (srcID >= 0 and srcID < self.n)

        # Implement Dijkstra's algorithm
        # Input:
        # self --> a reference to a MyGraph instance
        # srcID: the id of the source vertex.
        # Expected Output: (d,pi)
        #    d  --> Map each vertex id v to the distance from srcID
        #    pi --> Map each reachable vertex id v (except for srcID) to a parent.

        # Initialize the priority queue
        pq = PriorityQueue(self.n) #create the priority queue
        cur=self
        for i in range(0,self.n): # Iterate through all vertex ID
            if ( i == srcID):     # If ID is srcID
                pq.set(i,0.0)     # Distance of srcID should be zero
            else:                 # ID is not srcID
                pq.set(i, pq.Inf) # Distance should be infinity
        
        d = {}  # Initialize the map with distances to nodes
        pi = {} # Initialize the map with parents of vertices

        minKey, minDist=pq.extractMin()

        d[minKey]=minDist #set orignal source distance to 0
        pi[minKey]=minKey #set sources to orginal source



        while(pq.isEmpty()==False):# COMPLETE the Dijkstra code here

                lst=self.adjList[minKey]#grap array of lists of format (vertices,weight) for node minKey
                for n in lst:#loop through said list
                        
                        ##grap the next node attached to this node somehow
                        dist=n[1]+minDist#grab distance from list

                        node=n[0] #grab node from list
                        if(pq.hasKey(node)):#check if that nodes min dist has been found
                                if(pq.get(node)>dist):#check if path to the node from minKey is less then current path
                                        pq.set(node,dist)#set the nodes distance in the queue
                                        d[node]=dist#set the nodes distance in the return array
                                        pi[node]=minKey#sets the nodes parents

                minKey, minDist=pq.extractMin()#extract next node dont need to extract last node as all the paths will be filled would probably work better in a do while loop
                        

            
        return (d,pi)
Exemplo n.º 5
0
    def singleSourceShortestPath(self, srcID):
        assert (srcID >= 0 and srcID < self.n)
        # Implement Dijkstra's algorithm
        # Input:
        # self --> a reference to a MyGraph instance
        # srcID: the id of the source vertex.
        # Expected Output: (d,pi)
        #    d  --> Map each vertex id v to the distance from srcID
        #    pi --> Map each reachable vertex id v (except for srcID) to a parent.

        # Initialize the priority queue
        pq = PriorityQueue(self.n)  #create the priority queue

        for i in range(0, self.n):  # Iterate through all vertex ID
            if (i == srcID):  # If ID is srcID
                pq.set(i, 0.0)  # Distance of srcID should be zero
            else:  # ID is not srcID
                pq.set(i, pq.Inf)  # Distance should be infinity

        d = {}  # Initialize the map with distances to nodes
        pi = {}  # Initialize the map with parents of vertices

        # COMPLETE the Dijkstra code here
        if srcID == None or self.adjList[
                srcID] == None:  #make sure srcId is not None
            return
        Dist = 0.0
        for i in range(0, self.n):  #iniatialize dictionaries to default values
            d[i] = pq.Inf
            pi[i] = i
        d[srcID] = 0.0  #set source to zero
        while (not pq.isEmpty()):  #check if the queue is empty
            j = pq.extractMin(
            )  #tuple of min distance and vertex. j = (vertex,minDist)
            for i in self.adjList[j[0]]:
                if pq.hasKey(
                        i[0]
                ):  #assertion of pq.get(i) is that i must be in the priority queue
                    if i[1] + j[1] < pq.get(
                            i[0]
                    ):  #if distance of prior two nodes is less than current distance
                        Dist = j[1] + i[1]
                        pq.set(i[0], Dist)  #update distance at vertex to Dist
                        pi[i[0]] = j[0]  #map vertex to its parent
                        d[i[0]] = Dist  #map vertex to its new distance
        return (d, pi)
Exemplo n.º 6
0
    def singleSourceShortestPath(self, srcID):
        assert (srcID >= 0 and srcID < self.n)
        # Implement Dijkstra's algorithm
        # Input:
        # self --> a reference to a MyGraph instance
        # srcID: the id of the source vertex.
        # Expected Output: (d,pi)
        #    d  --> Map each vertex id v to the distance from srcID
        #    pi --> Map each reachable vertex id v (except for srcID) to a parent.

        # Initialize the priority queue
        pq = PriorityQueue(self.n)  #create the priority queue

        for i in range(0, self.n):  # Iterate through all vertex ID
            if (i == srcID):  # If ID is srcID
                pq.set(i, 0.0)  # Distance of srcID should be zero
            else:  # ID is not srcID
                pq.set(i, pq.Inf)  # Distance should be infinity

        d = {}  # Initialize the map with distances to nodes
        pi = {}  # Initialize the map with parents of vertices

        parent = None

        while not pq.isEmpty():
            minNode = pq.extractMin()
            if parent is None:
                d[minNode[0]] = minNode[1]
                pi[minNode[0]] = minNode[0]
            elif minNode[1] != pq.Inf:
                d[minNode[0]] = float(round(decimal.Decimal(minNode[1]), 2))
            else:
                d[minNode[0]] = pq.Inf

            lst = self.adjList[minNode[0]]
            for i in range(len(lst)):
                if pq.hasKey(lst[i][0]) and pq.get(
                        lst[i][0]) > lst[i][1] + d[minNode[0]]:
                    pi[lst[i][0]] = minNode[0]
                    pq.set(lst[i][0], lst[i][1] + d[minNode[0]])

            parent = minNode[0]

        return (d, pi)
Exemplo n.º 7
0
    def singleSourceShortestPath(self, srcID):
        assert (srcID >= 0 and srcID < self.n)
        # Implement Dijkstra's algorithm
        # Input:
        # self --> a reference to a MyGraph instance
        # srcID: the id of the source vertex.
        # Expected Output: (d,pi)
        #    d  --> Map each vertex id v to the distance from srcID
        #    pi --> Map each reachable vertex id v (except for srcID) to a parent.

        # Initialize the priority queue
        pq = PriorityQueue(self.n) #create the priority queue

        for i in range(0,self.n): # Iterate through all vertex ID
            if ( i == srcID):     # If ID is srcID
                pq.set(i,0.0)     # Distance of srcID should be zero
            else:                 # ID is not srcID
                pq.set(i, pq.Inf) # Distance should be infinity

        d = {}  # Initialize the map with distances to nodes
        pi = {} # Initialize the map with parents of vertices

        parent = None

        while not pq.isEmpty():
            minNode = pq.extractMin()
            if parent is None:
                d[minNode[0]] = minNode[1]
                pi[minNode[0]] = minNode[0]
            elif minNode[1] != pq.Inf:
                d[minNode[0]] = float(round(decimal.Decimal(minNode[1]), 2))
            else:
                d[minNode[0]] = pq.Inf

            lst = self.adjList[minNode[0]]
            for i in range(len(lst)):
                if pq.hasKey(lst[i][0]) and pq.get(lst[i][0]) > lst[i][1] + d[minNode[0]]:
                    pi[lst[i][0]] = minNode[0]
                    pq.set(lst[i][0], lst[i][1] + d[minNode[0]])

            parent = minNode[0]

        return (d,pi)
Exemplo n.º 8
0
    def singleSourceShortestPath(self, srcID):
        assert (srcID >= 0 and srcID < self.n)
        # Implement Dijkstra's algorithm
        # Input:
        # self --> a reference to a MyGraph instance
        # srcID: the id of the source vertex.
        # Expected Output: (d,pi)
        #    d  --> Map each vertex id v to the distance from srcID
        #    pi --> Map each reachable vertex id v (except for srcID) to a parent.

        # Initialize the priority queue
        pq = PriorityQueue(self.n) #create the priority queue
        
        for i in range(0,self.n): # Iterate through all vertex ID
            if ( i == srcID):     # If ID is srcID
                pq.set(i,0.0)     # Distance of srcID should be zero
            else:                 # ID is not srcID
                pq.set(i, pq.Inf) # Distance should be infinity
        
        d = {}  # Initialize the map with distances to nodes
        pi = {} # Initialize the map with parents of vertices
        
        # COMPLETE the Dijkstra code here
        
    # self.n : number of vertices in the graph
    # self.adjList: Adjacency list stored as a list of lists.
    #    self.adjList[i] stores all adjacent nodes to vertex ID i along with edge weights.
    # Eg., if vertex 2 has three edges (2,3) with weight 4.5, (2,4) with weight 3.2, and (2,5) with 2.1
    #    self.adjList[2] is the list [ (3,4.5), (4,3.2), (5,2.12) ]
    # your goal is to implement the singleSourceShortestPath function.
        while not pq.isEmpty():
            (n, dist) = pq.extractMin()
            d[n] = dist
            neighbors = self.adjList[n]
            for i in range (0, len(neighbors)):
                (v, e) = neighbors[i]
                if pq.hasKey(v):
                    oldDist = pq.get(v)		#is it more efficient if these constants are declared outside the loop?
                    newDist = dist + e
                    if newDist < oldDist:
                        pq.set(v, newDist)
                        pi[v] = n 
        return (d,pi)	
Exemplo n.º 9
0
    def singleSourceShortestPath(self, srcID):
        assert (srcID >= 0 and srcID < self.n
                )  # ensure that srcID is between 0 and size of graph.
        # Implement Dijkstra's algorithm
        # Input:
        # self --> a reference to a MyGraph instance
        # srcID: the id of the source vertex.
        # Expected Output: (d,pi)
        #    d  --> Map each vertex id v to the distance from srcID
        #    pi --> Map each reachable vertex id v (except for srcID) to a parent.

        # Initialize the priority queue
        pq = PriorityQueue(self.n)  #create the priority queue

        for i in range(0, self.n):  # Iterate through all vertex ID
            if i == srcID:  # If ID is srcID
                pq.set(i, 0.0)  # Distance of srcID should be zero
            else:  # ID is not srcID
                pq.set(i, pq.Inf)  # Distance should be infinity

        d = {}  # Initialize the map with distances to nodes
        pi = {}  # Initialize the map with parents of vertices

        while not pq.isEmpty():  # loop until priority queue is empty.
            (node, dist) = pq.extractMin()  # extract smallest dist node.
            d[node] = dist  # update dictionary with shortest distance.
            for (vertex, weight) in self.adjList[
                    node]:  # check the adjacency list of popped node.
                newDist = dist + weight  # calculate new distance.
                if pq.hasKey(
                        vertex
                ):  # if we haven't already popped the node in the adjacency list yet.
                    if newDist < pq.get(
                            vertex):  # check distance vs new calculated dist.
                        pq.set(vertex, newDist)  # update priority queue.
                        pi[vertex] = node  # update parent list.

        return (d, pi)
Exemplo n.º 10
0
    def singleSourceShortestPath(self, srcID):
        assert (srcID >= 0 and srcID < self.n)
        # Implement Dijkstra's algorithm
        # Input:
        # self --> a reference to a MyGraph instance
        # srcID: the id of the source vertex.
        # Expected Output: (d,pi)
        #    d  --> Map each vertex id v to the distance from srcID
        #    pi --> Map each reachable vertex id v (except for srcID) to a parent.

        # Initialize the priority queue
        pq = PriorityQueue(self.n)  #create the priority queue

        for i in range(0, self.n):  # Iterate through all vertex ID
            if (i == srcID):  # If ID is srcID
                pq.set(i, 0.0)  # Distance of srcID should be zero
            else:  # ID is not srcID
                pq.set(i, pq.Inf)  # Distance should be infinity

        d = {}  # Initialize the map with distances to nodes
        pi = {}  # Initialize the map with parents of vertices

        d[srcID] = 0  # first node to dist map since while won't catch it.

        while not pq.isEmpty():
            min = pq.extractMin()
            # Look at neighbors
            for neighbor in self.adjList[min[
                    0]]:  # where neighbor has not yet been removed from pq?
                alt = min[1] + neighbor[1]
                if pq.hasKey(neighbor[0]) and alt < pq.get(
                        neighbor[0]):  # previously stored needs to be replayed
                    # Update distances and parents everywhere
                    pq.set(neighbor[0], alt)
                    d[neighbor[0]] = alt
                    pi[neighbor[0]] = min[0]
        return (d, pi)
Exemplo n.º 11
0
    def singleSourceShortestPath(self, srcID):
        assert (srcID >= 0 and srcID < self.n)
        # Implement Dijkstra's algorithm
        # Input:
        # self --> a reference to a MyGraph instance
        # srcID: the id of the source vertex.
        # Expected Output: (d,pi)
        #    d  --> Map each vertex id v to the distance from srcID
        #    pi --> Map each reachable vertex id v (except for srcID) to a parent.

        # Initialize the priority queue
        pq = PriorityQueue(self.n) #create the priority queue

        for i in range(0,self.n): # Iterate through all vertex ID
            if ( i == srcID):     # If ID is srcID
                pq.set(i,0.0)     # Distance of srcID should be zero
            else:                 # ID is not srcID
                pq.set(i, pq.Inf) # Distance should be infinity

        d = {}  # Initialize the map with distances to nodes
        pi = {} # Initialize the map with parents of vertices

        #Code Starts HERE

        d[srcID] = 0 #Set distances from source equal to 0
        pi[srcID] = None #Set parents to None

        while not pq.isEmpty(): #While the priority queue is not empty
            (currentVertex,currentDistance) = pq.extractMin() #Extract the Min
            for (nextVertex, weight) in self.adjList[currentVertex]:
                newDist = weight + currentDistance
                if pq.hasKey(nextVertex): #Check if nextVertex exists in priority queue
                    if newDist < pq.get(nextVertex): #If the new distance is less
                        d[nextVertex] = newDist #Set new distnace
                        pi[nextVertex] = currentVertex #Set the parents
                        pq.set(nextVertex,newDist) #Set the new distance for the vertex
        return (d,pi)
Exemplo n.º 12
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class Sim:
    def __init__(self):
        self.q = PriorityQueue()
        self.time = 100
        self.nodes = {}
        self.actors = []
        self.done = False

    def add_actor(self, actor):
        actor.sim = self
        self.actors.append(actor)

    def at(self, event):
        if event.time < self.time:
            print "ERROR, time warp"
        else:
            self.q.put(event, event.time)

    def process(self):
        while not self.q.empty():
            event = self.q.get()
            self.time = event.time
            try:
                (result, actor) = event.process(self)
                actor.send(result)
            except StopIteration:
                pass
        print "Sim done"

    def prime(self):
        for a in self.actors:
            a.prime()

    def go(self):
        self.prime()
        self.process()
Exemplo n.º 13
0
def a_star_search(start, goal, moves):
    # Create the Frontier
    frontier = PriorityQueue()
    # add the start node to the frontier
    frontier.put(start, g_of_n(start) + h_of_n(start))
    # explore the node
    explored = explored_dic(len(start.item))
    # loop as long frontier is not empty
    while frontier.not_empty():
        # get the node with the highest priority
        state = frontier.get()
        # check if it's the goal then return the moves
        if state.item == goal:
            return state.moves
        # get the index of zero for the dictionary
        zero = state.item.index(0)
        # add the node to explored using
        explored[zero].add(tuple(state.item))
        # all possible moves for the current node
        for move in moves[zero]:
            # create new child adding to it the previous steps that taken to reach it
            new_child = State(state.moves[:], state.prevSteps + 1)
            # give it the new configuration
            new_child.create_item(move_list(move, state.item[:], zero))
            # get the zero index of the child
            zero2 = new_child.item.index(0)
            # check if it's already explored or added to the frontier
            if tuple(
                    new_child.item) in explored[zero2] or frontier.in_frontier(
                        tuple(new_child.item)):
                continue
            else:
                # add the new move to the child
                new_child.add_move(move)
                frontier.put(new_child, g_of_n(new_child) + h_of_n(new_child))
    return "nothing"
class Jeu():
    cpt = 0
    positions = {}
    caches = {}
    caches["l1"] = {}
    caches["l2"] = {}
    references = {}
    clock = 0
    strategie = CacheStrategie()

    def __init__(self, game, player, nom, init, goal, wallStates, goalStates):
        self.game = game
        self.player = player
        self.nom = nom
        self.position = init
        self.goal = goal
        self.graph = Graph((wallStates, goalStates),
                           game.spriteBuilder.rowsize,
                           game.spriteBuilder.colsize)
        self.chemin = []
        self.frontier = PriorityQueue()
        self.frontier.put(init, 0)
        self.came_from = {}
        self.cost_so_far = {}
        self.came_from[init] = None
        self.cost_so_far[init] = 0
        self.priority = 0
        self.avoid = []
        self.ID = Jeu.cpt
        Jeu.cpt += 1
        Jeu.positions[self.nom] = init
        Jeu.caches["l1"][self.nom] = []
        Jeu.references[self.nom] = self

    def play(self):
        i = 1
        while (not self.frontier.empty()):
            position, cout = self.frontier.get()

            if (position == self.goal):
                self.frontier.clear()
                break

            for nextP in self.graph.neighbors(position):
                new_cost = self.cost_so_far[position] + self.graph.cost(
                    position, nextP)
                if nextP not in self.cost_so_far or new_cost < self.cost_so_far[
                        nextP]:
                    self.cost_so_far[nextP] = new_cost
                    priority = new_cost + self.heuristic(self.goal, nextP)
                    self.frontier.put(nextP, priority)
                    self.came_from[nextP] = position
            i += 1

        result = self.path()
        result.reverse()
        self.chemin = result
        Jeu.strategie.apply(self)

    def reset(self):
        self.graph.wall = list(set(self.graph.wall) - set(self.avoid))
        self.chemin = []
        self.avoid.clear()
        self.frontier.clear()
        self.frontier.put(self.position, 0)
        self.came_from = {}
        self.cost_so_far = {}
        self.came_from[self.position] = None
        self.cost_so_far[self.position] = 0
        self.pause = 0
        Jeu.caches["l2"][self.nom] = self.caches["l1"][self.nom]
        Jeu.caches["l1"][self.nom] = []

    def done(self):
        for i in Jeu.references.values():
            if (i.goal != (-1, -1)):
                return False
        return True

    def heuristic(self, a, b):
        xa, ya = a
        xb, yb = b
        return abs(xa - xb) + abs(ya - yb)

    def path(self):
        final = []
        if (self.goal not in self.came_from):
            return final
        current = self.goal
        while (current != None):
            final.append(current)
            current = self.came_from[current]
        return final

    def freeze(self, n=1):
        self.priority += n

    def isObstacle(self, case):
        Jeu.positions[self.nom] = (-1, -1)
        temoin = case in Jeu.positions.values()
        Jeu.positions[self.nom] = self.position
        return temoin

    def move(self):
        if (Jeu.references[list(Jeu.references.keys())[0]] is self):
            Jeu.clock += 1
            print("clock", Jeu.clock)
        if (self.priority > 0):
            print(self.nom, "FREEEEEEEEEEEEZE")
            self.priority -= 1
            return
        # print("chemin: "+str(self.chemin))
        if (len(self.chemin) == 0):
            # print("joueur {0}: RIEN A CHERCHER".format(self.nom))
            Jeu.positions[self.nom] = self.position
            return
        if (self.isObstacle(self.chemin[0])):
            print("joueur {0}: conflit avec un autre joueur".format(self.nom))
            Jeu.strategie.reply(self)
            return
        Jeu.caches["l1"][self.nom].append(self.position)
        row, col = self.chemin[0]
        self.player.set_rowcol(row, col)
        self.position = (row, col)
        if (len(self.chemin) > 0):
            self.chemin.pop(0)
        Jeu.positions[self.nom] = self.position
        #print("pos :", self.nom, self.position)
        self.game.mainiteration()
Exemplo n.º 15
0
class Astar(WalkerBase):

    def __init__(self, maze):
        #super already sets the start as the current cell
        super(Astar, self).__init__(maze, maze.start())
        self.strategy = "Euclidean" #make it possible to choose an option which heuristic can be used
        #current position not necessary, stored in walker
        #open list containing all cells to explore
        self.open = PriorityQueue()
        self.closed = dict()# node:parent
        self.g = 10 #total costs the agent took so far
        self.last = None
        self.closed[self._cell] = None

    def heuristic(self,cell):
        '''

        :param currentPoint:
        :return: the distance (aka the costs) from the current point to reach the goal based on the current
                 heuristic
        '''
        return np.sqrt(np.square(maze_constants.XCELLS - cell._xLoc)+np.square(maze_constants.YCELLS - cell._yLoc))


    #Function tracking back to the last decision point, recursive?
    def backToDecisionPoint(self,cell):
        #paint the current cell which will be temporarily discarded
        self.paint(self._cell,TEMPORARILYDISCARDED_COLOR)
        self.last = self._cell
        self._cell = cell


    def step(self):
        if self._cell is self._maze.start():
            paths = self._cell.get_paths(last=self.last) #self._cell.parent where we came from
            for i in paths:
                costs = self.heuristic(self._cell) + self.g
                self.open.put([i,self._cell,0,self.g],costs)
                self.paint(i,OPENLIST_COLOR)
                self.last = self._cell

        #finished?
        if self._cell is self._maze.finish():
            road = []
            tmp = self._cell
            i = 0
            while not (tmp._yLoc == 0 and tmp._xLoc == 0):
                road.append(tmp)
                tmp = self.closed[tmp]
                i+=1
            road = road[::-1]

            for i in road:
                self.paint(i, FOUND_COLOR)

            self._isDone = True
            return

        #what are the possible steps from here?
        paths = self._cell.get_paths(last=self.last)

        #as long as there are cells in the open list,
        #  get the one with the lowest costs
        next = self.open.get()
        while next[0] in self.closed.keys():
            next = self.open.get()

        #continue the walk from where we are right now
        if next[1] == self._cell:
            self.paint(next[0],CLOSEDLIST_COLOR)
            self.closed[next[0]] = self._cell
            self._cell = next[0]
            self.g += 10

        #is the next cell an adjacent cell of the current cell?
        elif not next[0] in paths:
            #discard the current position
            self.paint(self._cell,TEMPORARILYDISCARDED_COLOR)
            self._cell = next[0]
            self.last = next[1]
            self.g = next[2]
            self.closed[self._cell] = self.last
            self.paint(self.last,CLOSEDLIST_COLOR)
            self.paint(self._cell,CLOSEDLIST_COLOR)

        #Append the open list for the current position
        newPaths = self._cell.get_paths(last=self.last)
        if len(newPaths) > 0:
            for i in newPaths:
                if not i in self.closed:
                    self.paint(i,OPENLIST_COLOR)
                    f = self.heuristic(i) + self.g
                    self.open.put([i,self._cell,self.g],f)
        if len(newPaths) == 0 and self.open.empty():
            print("This is not suppossed to happen, please start new")