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Add url and typing hint for BFS (#2156)

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* Add typing for bfs

* Add url for BFS

* rename the function

Co-authored-by: Christian Clauss <cclauss@me.com>

* Update graphs/bfs.py

Co-authored-by: Christian Clauss <cclauss@me.com>

* Change the return value type of bfs

* change the function name.

change all instances of bfs() to breadth_first_search().

* change the function name in annotate

* Add one more blank line.

* Delete one blank line.

* Delete one blank line.

I've read the https://www.flake8rules.com/rules/W391.html, and still don't know how to do it. I've tried using 0 ,1,2 blank lines...

* Update graphs/bfs.py

Co-authored-by: Christian Clauss <cclauss@me.com>

* Update graphs/bfs.py

Co-authored-by: Christian Clauss <cclauss@me.com>

* Rename bfs.py to breadth_first_search_2.py

Co-authored-by: Christian Clauss <cclauss@me.com>
This commit is contained in:
wuyudi 2020-06-25 23:54:41 +08:00 committed by GitHub
parent 3d4172307f
commit d2fa91b18e
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1 changed files with 9 additions and 10 deletions
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19
graphs/bfs.py → graphs/breadth_first_search_2.py
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@ -1,9 +1,7 @@
""" """
BFS. https://en.wikipedia.org/wiki/Breadth-first_search
pseudo-code: pseudo-code:
breadth_first_search(graph G, start vertex s):
BFS(graph G, start vertex s):
// all nodes initially unexplored // all nodes initially unexplored
mark s as explored mark s as explored
let Q = queue data structure, initialized with s let Q = queue data structure, initialized with s
@ -13,9 +11,10 @@ while Q is non-empty:
if w unexplored: if w unexplored:
mark w as explored mark w as explored
add w to Q (at the end) add w to Q (at the end)
""" """
from typing import Set, Dict
G = { G = {
"A": ["B", "C"], "A": ["B", "C"],
"B": ["A", "D", "E"], "B": ["A", "D", "E"],
@ -26,13 +25,13 @@ G = {
} }
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' 'ABCDEF'
""" """
explored, queue = set(), [start] # collections.deque([start]) explored = {start}
explored.add(start) queue = [start]
while queue: while queue:
v = queue.pop(0) # queue.popleft() v = queue.pop(0) # queue.popleft()
for w in graph[v]: for w in graph[v]:
@ -43,4 +42,4 @@ def bfs(graph, start):
if __name__ == "__main__": if __name__ == "__main__":
print(bfs(G, "A")) print(breadth_first_search(G, "A"))