Question

我有两个类PriorityQueue和PriorityQueueWithFunction，不能以任何方式更改，定义为：

class PriorityQueue:

    def __init__(self):
        self.heap = []
        self.count = 0

    def push(self, item, priority):
        entry = (priority, self.count, item)
        heapq.heappush(self.heap, entry)
        self.count += 1

    def pop(self):
        (_, _, item) = heapq.heappop(self.heap)
        return item

    def isEmpty(self):
        return len(self.heap) == 0


class PriorityQueueWithFunction(PriorityQueue):

    def __init__(self, priorityFunction):
        self.priorityFunction = priorityFunction
        PriorityQueue.__init__(self) # super-class initializer

我已经实现了一个使用PriorityQueueWithFunction类的A * Search算法。它需要两个参数。第一个是problem，它是搜索问题的抽象表示，其具有SearchAgent和Goal所在的起始状态。第二个参数是已经可以接受的 heuristic。这是我的实施：

def aStarSearch(problem, heuristic):
    closed = set() # A set to implement GraphSearch for efficiency

    # Two variables so that the passed function can recognize argument types before
    # they've been called
    node = problem.getStartState()
    cost = 0

    # Instantiate the real fringe. The function is cost + heuristic value
    fringe = PriorityQueueWithFunction(lambda x: cost + heuristic(node, problem))
    fringe.push((problem.getStartState(), 0, [])) # The first state with no cost or action

    while not fringe.isEmpty():
        node, cost, directions = fringe.pop()

        if problem.isGoalState(node):
            return directions

        if not (node in closed):
            closed.add(node)

            # getSuccessors(state) method expands all child nodes of node
            for node, direction, costOfStep in problem.getSuccessors(node):
                fringe.push((node, cost + costOfStep, directions + [direction]))

    if fringe.isEmpty():
        print "No solution was found."
        return []

我已经多次检查过这个实现，如果可能的话，它确实每次都找到了目标解决方案路径，但它找不到目标解决方案最佳。

我已经调试了这个问题，结果发现PriorityQueueWithFunction不像PriorityQueue那样。它取出了＆＃34;第一个＆＃34;而不是具有最低优先级整数的条目。

谁能告诉我这里有什么问题？我的实施会如何使我的PriorityQueueWithFunction行为好像是Queue而不是PriorityQueue？

为什么Python PriorityQueue没有弹出最低价值优先级？

0 个答案: