Graph Search: First working version & Shuffle problem

Graph-Search/cs412_bus_stops_a.py

@@ -8,14 +8,36 @@ Honor Code and Acknowledgments:
        Comments here on your code and submission.
 """
 
-from collections import deque
+from collections import defaultdict, deque
 
 
-def whatever_first_search(
-    graph: dict[str, set[str]], start: str, stop: str
-) -> list[str]:
+def whatever_first_search(graph: dict[str, set[str]], start: str, stop: str):
 
-    return []
+    bag: deque[tuple[str | None, str]] = deque()
+    bag.append((None, start))
+    visited: set[str] = set()
+    parent: dict[str, str | None] = {}
+
+    while len(bag) != 0:
+        parent_node, u = bag.pop()
+        if u in visited:
+            continue
+        visited.add(u)
+        parent[u] = parent_node
+
+        if u == stop:
+            path: list[str] = []
+            while u is not None:
+                path.append(u)
+                u = parent[u]
+            path.reverse()
+            return path
+
+        for v in graph[u]:
+            if v not in visited:
+                bag.append((u, v))
+
+    return None
 
 
 # All modules for CS 412 must include a main method that allows it
@@ -23,21 +45,18 @@ def whatever_first_search(
 def main():
     n: int = int(input())
 
-    graph: dict[str, set[str]] = {}
+    graph: dict[str, set[str]] = defaultdict(set)
 
     for _ in range(0, n):
         u, v = input().split()
-
-        if u not in graph:
-            graph[u] = set([v])
-        else:
-            graph[u].add(v)
+        graph[u].add(v)
+        graph[v].add(u)
 
     target = input().split()
 
     path = whatever_first_search(graph, target[0], target[1])
 
-    if len(path) == 0:
+    if path is None:
         print("no route possible")
     else:
         print(" ".join(path))