Add a naive recursive implementation of 0-1 Knapsack Problem (#2743)

* Add naive recursive implementation of 0-1 Knapsack problem

* Fix shadowing

* Add doctest

* Fix type hints

* Add link to wiki

* Blacked the file

* Fix isort

* Move knapsack / add readme and more tests

* Add missed main in tests

knapsack/test_knapsack.py

@@ -0,0 +1,52 @@
+"""
+Created on Fri Oct 16 09:31:07 2020
+
+@author: Dr. Tobias Schröder
+@license: MIT-license
+
+This file contains the test-suite for the knapsack problem.
+"""
+import unittest
+
+from knapsack import knapsack as k
+
+
+class Test(unittest.TestCase):
+    def test_base_case(self):
+        """
+        test for the base case
+        """
+        cap = 0
+        val = [0]
+        w = [0]
+        c = len(val)
+        self.assertEqual(k.knapsack(cap, w, val, c), 0)
+
+        val = [60]
+        w = [10]
+        c = len(val)
+        self.assertEqual(k.knapsack(cap, w, val, c), 0)
+
+    def test_easy_case(self):
+        """
+        test for the base case
+        """
+        cap = 3
+        val = [1, 2, 3]
+        w = [3, 2, 1]
+        c = len(val)
+        self.assertEqual(k.knapsack(cap, w, val, c), 5)
+
+    def test_knapsack(self):
+        """
+        test for the knapsack
+        """
+        cap = 50
+        val = [60, 100, 120]
+        w = [10, 20, 30]
+        c = len(val)
+        self.assertEqual(k.knapsack(cap, w, val, c), 220)
+
+
+if __name__ == "__main__":
+    unittest.main()