Python code for depth first search. rev1.

Author: joeyajames

DepthFirstSearch.py

@@ -0,0 +1,72 @@
+class Vertex:
+	def __init__(self, n):
+		self.name = n
+		self.neighbors = list()
+		
+		self.discovery = 0
+		self.finish = 0
+		self.color = 'black'
+	
+	def add_neighbor(self, v):
+		nset = set(self.neighbors)
+		if v not in nset:
+			self.neighbors.append(v)
+			self.neighbors.sort()
+
+class Graph:
+	vertices = {}
+	time = 0
+	
+	def add_vertex(self, vertex):
+		if isinstance(vertex, Vertex) and vertex.name not in self.vertices:
+			self.vertices[vertex.name] = vertex
+			return True
+		else:
+			return False
+	
+	def add_edge(self, u, v):
+		if u in self.vertices and v in self.vertices:
+			for key, value in self.vertices.items():
+				if key == u:
+					value.add_neighbor(v)
+				if key == v:
+					value.add_neighbor(u)
+			return True
+		else:
+			return False
+			
+	def print_graph(self):
+		for key in sorted(list(self.vertices.keys())):
+			print(key + str(self.vertices[key].neighbors) + "  " + str(self.vertices[key].discovery) + "/" + str(self.vertices[key].finish))
+
+	def _dfs(self, vertex):
+		global time
+		vertex.color = 'red'
+		vertex.discovery = time
+		time += 1
+		for v in vertex.neighbors:
+			if self.vertices[v].color == 'black':
+				self._dfs(self.vertices[v])
+		vertex.color = 'blue'
+		vertex.finish = time
+		time += 1
+		
+	def dfs(self, vertex):
+		global time
+		time = 1
+		self._dfs(vertex)
+			
+g = Graph()
+# print(str(len(g.vertices)))
+a = Vertex('A')
+g.add_vertex(a)
+g.add_vertex(Vertex('B'))
+for i in range(ord('A'), ord('K')):
+	g.add_vertex(Vertex(chr(i)))
+
+edges = ['AB', 'AE', 'BF', 'CG', 'DE', 'DH', 'EH', 'FG', 'FI', 'FJ', 'GJ', 'HI']
+for edge in edges:
+	g.add_edge(edge[:1], edge[1:])
+	
+g.dfs(a)
+g.print_graph()