Add url and typing hint for BFS

graphs/bfs.py

@@ -1,8 +1,6 @@
-"""
+"""https://en.wikipedia.org/wiki/Breadth-first_search
 BFS.
-
 pseudo-code:
-
 BFS(graph G, start vertex s):
 // all nodes initially unexplored
 mark s as explored
@@ -13,9 +11,10 @@
  if w unexplored:
  mark w as explored
  add w to Q (at the end)
-
 """
 
+from typing import Set, Dict
+
 G = {
  "A": ["B", "C"],
  "B": ["A", "D", "E"],
@@ -26,13 +25,13 @@
 }
 
 
-def bfs(graph, start):
+def breadth_first_search(graph: Dict, start: str) -> Set[str]:
  """
- >>> ''.join(sorted(bfs(G, 'A')))
+ >>> ''.join(sorted(breadth_first_search(G, 'A')))
  'ABCDEF'
  """
- explored, queue = set(), [start] # collections.deque([start])
- explored.add(start)
+ explored = {start}
+ queue = [start]
  while queue:
  v = queue.pop(0) # queue.popleft()
  for w in graph[v]:
@@ -43,4 +42,4 @@ def bfs(graph, start):
 
 
 if __name__ == "__main__":
- print(bfs(G, "A"))
+ print(breadth_first_search(G, "A"))