Add coding exercises for Facebook interviews

Add attempts at solving coding problems to Briefcase.

scratch/facebook/word-cloud.py

@@ -0,0 +1,32 @@
+def normalize(x):
+    noise = ".,;-"
+    for y in noise:
+        if x.endswith(y):
+            return normalize(x[0:-1])
+        if x.startswith(y):
+            return normalize(x[1:])
+    return x.lower()
+
+def word_cloud(xs):
+    result = dict()
+
+    for x in xs.split(' '):
+        k = normalize(x)
+        if k in result:
+            result[k] += 1
+        else:
+            result[k] = 1
+
+    return result
+
+result = word_cloud("This is just the beginning. The UK will lockdown again.")
+assert result.get('this') == 1
+assert result.get('is') == 1
+assert result.get('just') == 1
+assert result.get('the') == 2
+assert result.get('beginning') == 1
+assert result.get('uk') == 1
+assert result.get('will') == 1
+assert result.get('lockdown') == 1
+assert result.get('again') == 1
+print("Success!")