Question

我正在尝试创建A Star算法并将其应用于游戏Snake。我遇到的问题是，我从未在窗口上绘制任何东西，因为它从未到达该代码。尝试在方法run（）中计算路径时，它会卡住。具体来说，开放集永远不会为零，它会添加已经存在的节点。

我尝试将各种列表打印到控制台，但是我发现的是，“当前”在随机点重复显示图块，而“ openSet”和“ closedSet”随着这些重复的图块继续变大。我们还测试了我的Tile对象，我的contains方法和我的GiveNeighbors方法，所有这些似乎都可以正常工作并给出了预期的结果。另外，作为参考，我将使用以下伪代码：https://en.wikipedia.org/wiki/A*_search_algorithm < / p>

import Tile
import pygame

class A_star:
def __init__(self):
    self.closedSet = []
    self.openSet = []


def run(self, start, goal):

    self.closedSet = []
    self.openSet = [start]
    path = []

    #THE LENGTH OF OPEN SET NEVER GOES TO ZERO!
    while len(self.openSet) > 0:
        #Set current to node in openSet with lowest fscore
        current = self.openSet[0]
        currindex = 0
        for i, node in enumerate(self.openSet):
            if node.fScore < current.fScore:
                current = node
                currindex = i

        #romove from Open set and add to closed
        self.openSet.pop(currindex)
        self.closedSet.append(current)

        #Reached the end        
        if current.tileEquals(goal):
            print("Done")
            while current != None:
                path.append(current)
                current = current.cameFrom
            return path[::-1]

        neighbors = self.giveNeighbors(current)

        print("Current: " + str(current.posx) + ", " + str(current.posy))

        print("Neighbors")
        for i in neighbors:
            print(str(i.posx) + ", " + str(i.posy))

        for i in neighbors:
            #if neighbor is already checked, then ignore it.
            if not self.contains(self.closedSet, i):
                #Distance between start adn neighbor. tenative gscore
                tempGScore = current.gScore + 1

                #if neighbor is not in openset. Discovered a new node!
                if not self.contains(self.openSet, i):
                    self.openSet.append(i)
                elif tempGScore < i.gScore:
                    i.gScore = tempGScore
                    i.cameFrom = current
                    i.fScore = i.gScore + self.heuristicCost(i, goal) #f = g + h

        print("Open:")
        for i in self.openSet:
            print(str(i.posx) + ", " + str(i.posy))
        print("Closed")
        for i in self.closedSet:
            print(str(i.posx) + ", " + str(i.posy))


#Calculates the estimated distance from a given tile to end
def heuristicCost(self, neighbor, goal):
    #The snake never goes diagonal, therefore calculate manhatten distance
    distance = abs(neighbor.posx - goal.posx) + abs(neighbor.posy - goal.posy)
    return distance

def giveNeighbors(self, current):
    neighbors = []
    if current.posx > 0:
        neighbors.append(Tile(current.posx - 10, current.posy))
    if current.posx < 200:
        neighbors.append(Tile(current.posx + 10, current.posy))
    if current.posy > 0:
        neighbors.append(Tile(current.posx, current.posy - 10))
    if current.posy < 200:
        neighbors.append(Tile(current.posx, current.posy + 10))

    return neighbors

def contains(self, s, tile):
 for i in s:
    if i.tileEquals(tile):
        return True
    else:
        return False



def testAStar():
pygame.init()
window = pygame.display.set_mode((200, 200))
pygame.display.set_caption("AStar Test")
window.fill((255,255,255))
clock = pygame.time.Clock()

start = Tile(0, 0)
end = Tile(190, 190)

astar = A_star()
path = astar.run(start, end)

run = True
while run:

    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            run = False

    pygame.draw.rect(window, (0, 255, 0), (start.posx, start.posy, 10, 10))
    pygame.draw.rect(window, (255, 0, 0), (end.posx, end.posy, 10, 10))


    for i in path:
        pygame.draw.rect(window, (0, 0, 255), (i.posx, i.posy, 10, 10))

    print("drew stuff")

    pygame.display.update()
    window.fill((255,255,255))
    clock.tick(10)

pygame.quit()


if __name__== "__main__":
    testAStar()


class Tile:
    def __init__(self, x, y):
            self.posx = x
            self.posy = y
            self.fScore = 0
            self.gScore = 0
            self.cameFrom = None

    def nextTileRight(self):
            self.posx = self.posx + 10

    def nextTileDown(self):
            self.posy = self.posy + 10

    def nextTileUp(self):
            self.posy = self.posy - 10

    def nextTileLeft(self):
            self.posx = self.posx - 10

    def tileEquals(self, t):
            if self.posx == t.posx and self.posy == t.posy:
                return True
            else:
                return False

预期结果应该是在窗口上从起始节点到终止节点绘制的非对角线路径。（此外，如果我的缩进不正确，对不起。我对该网站仍然很陌生）

Answer 1

我不确定为什么要检查openSets == 0，是否要寻找currentNode = destination或所有邻居均已关闭，这意味着所有内容均已检查且未找到路径。

为什么开放集永远不会变为0？

1 个答案: