Added example solutions to several chapters. Feel free to create a pull request with your answers. Also for the chapters that have no solutions yet :)

CH_05_functional_programming/exercise_01/solution_00.py

@@ -0,0 +1,29 @@
+# Implement the quicksort algorithm.
+import random
+
+# one-liner approach
+qs = lambda xs: xs if len(xs) <= 1 else qs(
+    [x for x in xs[1:] if x < xs[0]]) + [xs[0]] + qs(
+    [x for x in xs[1:] if x >= xs[0]])
+
+
+# more verbose approach
+def quicksort(xs):
+    if len(xs) <= 1:
+        return xs
+    else:
+        left = quicksort([x for x in xs[1:] if x < xs[0]])
+        right = quicksort([x for x in xs[1:] if x >= xs[0]])
+        middle = [xs[0]]
+        return left + middle + right
+
+
+def main():
+    # test
+    xs = random.sample(range(1000), 100)
+    assert quicksort(xs) == sorted(xs)
+    assert qs(xs) == sorted(xs)
+
+
+if __name__ == '__main__':
+    main()