【python3数据结构】图Graph及DFS（深度优先搜索）BFS（广度优先搜索）

Graph 和 Vertex 构建基于邻接列表：

# -*- coding: utf-8 -*-
# @Date   : 2019/12/1
# @File   : AdjListGraph.pyimport sysclass Vertex(object):def __init__(self, node):self.id = nodeself.adjacent = {} # 存该节点的邻居及其边权重self.distance = sys.maxsizeself.visited = Falseself.previous = Nonedef addNeighbor(self, neighbor, weight=0):self.adjacent[neighbor] = weightdef getConnections(self):return self.adjacent.keys()def getVertexID(self):return self.iddef setVertexID(self, id):self.id = iddef getWeight(self, neighbor):return self.adjacent.get(neighbor)def setDistance(self, dist):self.distance = distdef getDistance(self):return self.distancedef setPrevious(self, prev):self.previous = prevdef setVisited(self):self.visited = True# 打印节点时显示的信息def __str__(self):return str(self.id) + " adjacent: " + str([x.id for x in self.adjacent])def __lt__(self, other):return self.distance < other.distance and self.id < other.idclass Graph(object):def __init__(self, directed=False):self.vertexDict = {} # key:id  value:Vertex(id)self.numVertices = 0self.directed = directeddef __iter__(self):return iter(self.vertexDict.values())def isDirected(self):return self.directeddef vertexCount(self):return self.numVerticesdef addVertex(self, node):self.numVertices = self.numVertices + 1newVertex = Vertex(node)self.vertexDict[node] = newVertexreturn newVertexdef getVertex(self, n):return self.vertexDict.get(n)def addEdge(self, frm, to, cost=0):if frm not in self.vertexDict:self.addVertex(frm)if to not in self.vertexDict:self.addVertex(to)self.vertexDict[frm].addNeighbor(self.vertexDict[to], cost)if not self.directed:self.vertexDict[to].addNeighbor(self.vertexDict[frm], cost)def getVertices(self):# return idsreturn self.vertexDict.keys()# def setPrevious(self, current):#     self.previous = current## def getPrevious(self, current):#     return self.previousdef getEdges(self):edges = []for key, currentVertex in self.vertexDict.items():for neighbor in currentVertex.getConnections():currentVertexID = currentVertex.getVertexID()neighborID = neighbor.getVertexID()edges.append((currentVertexID, neighborID, currentVertex.getWeight(neighbor)))return edgesdef getNeighbors(self, v):vertex = self.vertexDict[v]return vertex.getConnections()if __name__ == '__main__':G = Graph(True)G.addVertex('a')G.addVertex('b')G.addVertex('c')G.addVertex('d')G.addVertex('e')G.addVertex('f')G.addEdge('a', 'b', 1)G.addEdge('a', 'c', 1)G.addEdge('b', 'd', 1)G.addEdge('b', 'e', 1)G.addEdge('c', 'd', 1)G.addEdge('c', 'e', 1)G.addEdge('d', 'e', 1)G.addEdge('e', 'a', 1)print(G.getEdges())for k in G.getEdges():print(k)print()for key in G.vertexDict:# 对应 Vertex中的__str__print(key, 'corresponds to', G.vertexDict[key])print()v = 'a'neighbors = G.getNeighbors(v)for n in neighbors:print(n)# 基于边的结合构建图def graphFromEdgeList(E, directed=False):"""Make a graph instance based on a sequence of edge tuples.Edges can be either of from (origin,destination) or(origin,destination,element). Vertex set is presume to be thoseincident to at least one edge.vertex labels are assumed to be hashable."""g = Graph(directed)# 得到所有节点名称V = set()for e in E:V.add(e[0])V.add(e[1])print("Vertex :", V)# 构建图节点vertexvertices = {}for v in V:vertices[v] = g.addVertex(v)print(g.vertexCount())# 根据边集合为节点添加边for e in E:src = e[0]dest = e[1]cost = e[2] if len(e) > 2 else Noneg.addEdge(src, dest, cost)return gE2 = (('A', 'B', 1), ('A', 'C', 1),)graph = graphFromEdgeList(E2, True)for k in graph.getEdges():print(k)print()E = (('SFO', 'LAX', 337), ('SFO', 'BOS', 2704), ('SFO', 'ORD', 1846),('SFO', 'DFW', 1464), ('LAX', 'DFW', 1235), ('LAX', 'MIA', 2342),('DFW', 'ORD', 802), ('DFW', 'MIA', 1121), ('ORD', 'BOS', 867),('ORD', 'JFK', 740), ('MIA', 'JFK', 1090), ('MIA', 'BOS', 1258),('JFK', 'BOS', 187),)graph = graphFromEdgeList(E, True)for e in graph.getEdges():print(e)for m in graph.getVertices():print(m)

DFS:

# -*- coding: utf-8 -*-
# @Date   : 2019/12/1
# @File   : DepthFirstSearch.pyfrom AdjListGraph import Graph, Vertexdef __dfsHelper(s, G, visited, parents):# if s == G:#     returnif s not in visited:visited[s.getVertexID()] = Trueprint("traversal: ", s.getVertexID())for neighbor in s.getConnections():if neighbor.getVertexID() not in visited:parents[neighbor.getVertexID()] = s.getVertexID()__dfsHelper(neighbor, G, visited, parents)# print(parents)def DFSRecursive(G):visited = {}parents = {}for node in G:if node.getVertexID() not in visited:__dfsHelper(node, G, visited, parents)print(visited)print(parents)def DFSIterative(G, start, dest):stack = []parents = {}visited = set()stack.append(start)while stack:node = stack.pop()print("traversal: ", node.getVertexID())if node.getVertexID() == dest.getVertexID():return parents# if node not in visited:visited.add(node.getVertexID())for neighbor in G.getNeighbors(node.getVertexID()):if neighbor not in visited:stack.append(neighbor)parents[neighbor.getVertexID()] = node.getVertexID()return Noneif __name__ == '__main__':G = Graph(directed=True)G.addVertex('a')G.addVertex('b')G.addVertex('c')G.addVertex('d')G.addVertex('e')G.addVertex('f')G.addEdge('a', 'b', 1)G.addEdge('a', 'c', 1)G.addEdge('b', 'd', 1)G.addEdge('b', 'e', 1)G.addEdge('c', 'd', 1)G.addEdge('c', 'e', 1)G.addEdge('d', 'e', 1)G.addEdge('e', 'a', 1)G.addEdge('a', 'f', 1)print(G.getEdges())for k in G.getEdges():print(k)visited = {}parents = {}DFSRecursive(G)print()# 从v节点开始遍历v = G.getVertex('e')__dfsHelper(v, G, visited, parents)#print("#"*20)start = G.getVertex('a')dest = G.getVertex('e')print(DFSIterative(G, start=start, dest=dest))

BFS:

# -*- coding: utf-8 -*-
# @Date   : 2019/12/1
# @File   : BreadthFirstSearch.pyfrom AdjListGraph import Graph
from collections import dequedef BFSIterative(G, start, dest):queue = deque()visited = set()parents = {}queue.append(start)while queue:node = queue.popleft()print("visiting :", node.getVertexID())if node.getVertexID() == dest.getVertexID():return parentsvisited.add(node.getVertexID())for neighbor in G.getNeighbors(node.getVertexID()):if neighbor not in visited:queue.append(neighbor)parents[neighbor.getVertexID()] = node.getVertexID()return Noneif __name__ == '__main__':G = Graph(directed=True)G.addVertex('a')G.addVertex('b')G.addVertex('c')G.addVertex('d')G.addVertex('e')G.addVertex('f')G.addEdge('a', 'b', 1)G.addEdge('a', 'c', 1)G.addEdge('a', 'f', 1)G.addEdge('b', 'd', 1)G.addEdge('b', 'e', 1)G.addEdge('c', 'd', 1)G.addEdge('c', 'e', 1)G.addEdge('d', 'e', 1)G.addEdge('e', 'a', 1)print(G.getEdges())for k in G.getEdges():print(k)#print("#" * 20)start = G.getVertex('a')dest = G.getVertex('e')print(BFSIterative(G, start=start, dest=dest))

DFS vs BFS:

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【python3数据结构】图Graph及DFS（深度优先搜索）BFS（广度优先搜索）

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