Add coding exercises for Facebook interviews

Add attempts at solving coding problems to Briefcase.

scratch/facebook/recursion-and-dynamic-programming/paint-fill.py

@@ -0,0 +1,36 @@
+from collection import deque
+
+def fill(point, canvas, color):
+    if x not in canvas:
+        return
+    elif y not in canvas[x]:
+        return
+
+    x, y = point
+    if canvas[y][x] == color:
+        return
+    canvas[y][x] = color
+    fill((x + 1, y), canvas, color)
+    fill((x - 1, y), canvas, color)
+    fill((x, y + 1), canvas, color)
+    fill((x, y - 1), canvas, color)
+
+def fill_bfs(point, canvas, color):
+    x, y = point
+    if x not in canvas:
+        return None
+    if y not in canvas[x]:
+        return None
+    xs = deque()
+    xs.append((x, y))
+    while xs:
+        x, y = xs.popleft()
+        canvas[y][x] = color
+        for x2, y2 in [(x - 1, y), (x + 1, y), (x, y - 1), (x, y + 1)]:
+            if x2 not in canvas:
+                continue
+            elif y2 not in canvas[x2]:
+                continue
+            if canvas[y2][x2] != color:
+                xs.append((x2, y2))
+    return None