Added Breadth First Search

Author: OmkarPathak

pygorithm/searching/breadth_first_search.py

@@ -0,0 +1,23 @@
+# Author: OMKAR PATHAK
+# Created On: 1st August 2017
+
+#  breadth first search algorithm
+def bfs(graph, startVertex):
+    # Take a list for stoting already visited vertexes
+    if startVertex not in graph or graph[startVertex] is None or graph[startVertex] == []:
+        return None
+
+    # create a list to store all the vertexes for BFS and a set to store the visited vertices
+    visited, queue = set(), [startVertex]
+
+    while queue:
+        vertex = queue.pop(0)
+        if vertex not in visited:
+            visited.add(vertex)
+            queue.extend(graph[vertex] - visited)
+            
+    return visited
+
+# time complexities
+def time_complexities():
+    return '''O(V + E) where V = Number of vertices and E = Number of Edges'''