no message

Author: Chris Wu

problems/flood-fill.py

@@ -14,4 +14,14 @@ def floodFill(self, image, sr, sc, newColor):
             if j+1<len(image[0]): stack.append((i, j+1))
             if 0<=j-1: stack.append((i, j-1))
 
-        return image
+        return image
+
+"""
+DFS the `image`.
+If the color is newColor, we don't need to see.
+If the color is not originalColor, we don't need to see, too.
+Else we paint the node to newColor.
+
+Time: O(N).
+Space: O(1).
+"""

problems/keys-and-rooms.py

@@ -0,0 +1,20 @@
+class Solution(object):
+    def canVisitAllRooms(self, rooms):
+        if not rooms: return True
+        
+        visited = set()
+        stack = [0]
+
+        while stack:
+            key = stack.pop()
+            if key in visited: continue
+            visited.add(key)
+            stack.extend(rooms[key])
+
+        return len(rooms)==len(visited)
+
+"""
+Time: O(N).
+Space: O(N).
+N is the number of rooms.
+"""