• python数据结构与算法——图的广度优先和深度优先的算法


    根据维基百科的伪代码实现:

    广度优先BFS:

    使用队列集合

    标记初始结点已被发现,放入队列

    每次循环从队列弹出一个结点

    将该节点的所有相连结点放入队列,并标记已被发现

    通过队列,将迷宫路口所有的门打开,从一个门进去继续打开里面的门,然后返回前一个门处

     1 """
     2  procedure BFS(G,v) is
     3      let Q be a queue
     4      Q.enqueue(v)
     5      label v as discovered
     6      while Q is not empty
     7         v ← Q.dequeue()
     8         procedure(v)
     9         for all edges from v to w in G.adjacentEdges(v) do
    10             if w is not labeled as discovered
    11                 Q.enqueue(w)
    12                 label w as discovered
    13 """
    14 def procedure(v):
    15     pass
    16 
    17 def BFS(G,v0):
    18     """ 广度优先搜索 """
    19     q, s = [], set()
    20     q.extend(v0)
    21     s.add(v0)
    22     while q:    # 当队列q非空
    23         v = q.pop(0)
    24         procedure(v)
    25         for w in G[v]:     # 对图G中顶点v的所有邻近点w 
    26             if w not in s: # 如果顶点 w 没被发现
    27                 q.extend(w)
    28                 s.add(w)    # 记录w已被发现

    深度优先DFS

    使用 集合

    初始结点入栈

    每轮循环从栈中弹出一个结点,并标记已被发现

    对每个弹出的结点,将其连接的所有结点放到队列中

    通过栈的结构,一步步深入挖掘

     1 """"
     2 Pseudocode[edit]
     3 Input: A graph G and a vertex v of G
     4 
     5 Output: All vertices reachable from v labeled as discovered
     6 
     7 A recursive implementation of DFS:[5]
     8 
     9 1  procedure DFS(G,v):
    10 2      label v as discovered
    11 3      for all edges from v to w in G.adjacentEdges(v) do
    12 4          if vertex w is not labeled as discovered then
    13 5              recursively call DFS(G,w)
    14 A non-recursive implementation of DFS:[6]
    15 
    16 1  procedure DFS-iterative(G,v):
    17 2      let S be a stack
    18 3      S.push(v)
    19 4      while S is not empty
    20 5            v = S.pop() 
    21 6            if v is not labeled as discovered:
    22 7                label v as discovered
    23 8                for all edges from v to w in G.adjacentEdges(v) do
    24 9                    S.push(w)
    25 """
    26 
    27 def DFS(G,v0):
    28     S = []
    29     S.append(v0)
    30     label = set()
    31     while S:
    32         v = S.pop()
    33         if v not in label:
    34             label.add(v)
    35             procedure(v)
    36             for w in G[v]:
    37                 S.append(w)
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  • 原文地址:https://www.cnblogs.com/hanahimi/p/4692601.html
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