Adding solution to challenge '841. Keys and Rooms' (medium).

Author: rboyd

medium/keys-and-rooms/keys-and-rooms.py

@@ -0,0 +1,10 @@
+class Solution:
+    def canVisitAllRooms(self, rooms: List[List[int]]) -> bool:
+        keychain = {0}
+        def dfs(room_num):
+            for key in rooms[room_num]:
+                if key not in keychain:
+                    keychain.add(key)
+                    dfs(key)
+        dfs(0)
+        return len(keychain) == len(rooms)