added new BFS code

Author: joeyajames

bfs.py

@@ -0,0 +1,71 @@
+class Vertex:
+	def __init__(self, n):
+		self.name = n
+		self.neighbors = list()
+		
+		self.distance = 9999
+		self.color = 'black'
+	
+	def add_neighbor(self, v):
+		if v not in self.neighbors:
+			self.neighbors.append(v)
+			self.neighbors.sort()
+
+class Graph:
+	vertices = {}
+	
+	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].distance))
+		
+	def bfs(self, vert):
+		q = list()
+		vert.distance = 0
+		vert.color = 'red'
+		for v in vert.neighbors:
+			self.vertices[v].distance = vert.distance + 1
+			q.append(v)
+		
+		while len(q) > 0:
+			u = q.pop(0)
+			node_u = self.vertices[u]
+			node_u.color = 'red'
+			
+			for v in node_u.neighbors:
+				node_v = self.vertices[v]
+				if node_v.color == 'black':
+					q.append(v)
+					if node_v.distance > node_u.distance + 1:
+						node_v.distance = node_u.distance + 1
+					
+g = Graph()
+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.bfs(a)
+g.print_graph()