Create bfs.py

bfs.py

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+from graph_directed import Graph #importing graph from previous chapter but directed version
+from graph_directed import Node #see code of previous chapter
+from graph_directed import Color
+
+q = [] #queue for BFS
+
+def enqueue(n):
+    global q
+    q = [n]+q
+
+def dequeue():
+    global q
+    temp = q[len(q)-1]
+    del(q[len(q)-1])
+    return temp
+
+def bfs(g):
+    s = g.heads[0]
+
+    for i in range(0, g.number_of_vertices):
+        g.heads[i].color = Color.White
+    s.color = Color.Gray
+
+    enqueue(s)
+
+    while(len(q)>0):
+        u = dequeue()
+        temp = u.head
+        while(temp != None):
+            if(g.heads[temp.index_of_item].color == Color.White):
+                g.heads[temp.index_of_item].color = Color.Gray
+                enqueue(g.heads[temp.index_of_item])
+            temp = temp.next
+        u.color = Color.Black
+        print(u.data)
+
+if __name__ == '__main__':
+    g = Graph(7)
+
+    g.add_edge(1, 2)
+    g.add_edge(1, 5)
+    g.add_edge(1, 3)
+    g.add_edge(2, 6)
+    g.add_edge(2, 4)
+    g.add_edge(5, 4)
+    g.add_edge(3, 4)
+    g.add_edge(3, 7)
+
+    bfs(g)