Add coding exercises for Facebook interviews

Add attempts at solving coding problems to Briefcase.

scratch/facebook/shuffle.py

@@ -0,0 +1,17 @@
+from random import randint
+
+def get_random(i, j):
+    return randint(i, j)
+
+def shuffle(xs):
+    for i in range(len(xs)):
+        j = get_random(i, len(xs) - 1)
+        xs[i], xs[j] = xs[j], xs[i]
+
+xs = list(range(1, 53))
+print(xs)
+assert len(set(xs)) == 52
+shuffle(xs)
+assert len(set(xs)) == 52
+print(xs)
+print("Success!")