feat: more statistics + a simple exercise

tests/test_essentials.py

@@ -0,0 +1,19 @@
+import pytest
+
+from src.modules.exercises.essentials import *
+
+def test_subarray_sum():
+	input = [2,3,-8,7,-1,2,3]
+	result = maximum_subarray_sum(input)
+	expected = [11, [7, -1, 2, 3]]
+	assert result == expected
+	input = [-2,-4]
+	result = maximum_subarray_sum(input)
+	expected = [-2, [-2]]
+	assert result == expected
+	input = [5,4,1,7,8]
+	result = maximum_subarray_sum(input)
+	expected = [25, [5,4,1,7,8]]
+	assert result == expected
+
+