bfs.md

BFS Searching

• 前置知识：Basic, AStar

1. 核心算法流程

核心算法流程实际上与AStar算法一致，只不过$h(x)$变成了0

2. 代码分析

    def searching(self):
        """
        Breadth-first Searching.
        :return: path, visited order
        """

        self.PARENT[self.s_start] = self.s_start
        self.g[self.s_start] = 0
        self.g[self.s_goal] = math.inf
        heapq.heappush(self.OPEN,
                       (0, self.s_start))

        while self.OPEN:
            _, s = heapq.heappop(self.OPEN)
            self.CLOSED.append(s)

            if s == self.s_goal:
                break

            for s_n in self.get_neighbor(s):
                new_cost = self.g[s] + self.cost(s, s_n)

                if s_n not in self.g:
                    self.g[s_n] = math.inf

                if new_cost < self.g[s_n]:  # conditions for updating Cost
                    self.g[s_n] = new_cost
                    self.PARENT[s_n] = s

                    # bfs, add new node to the end of the openset
                    prior = self.OPEN[-1][0]+1 if len(self.OPEN)>0 else 0
                    heapq.heappush(self.OPEN, (prior, s_n))

        return self.extract_path(self.PARENT), self.CLOSED

代码是用堆来实现的。

3. 效果

图1：BFS效果图展示