feat(dp): house robber

algorithms/dynamic_programming/house_robber/README.md

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+# House Robber
+
+You are a professional robber planning to rob houses along a street. Each house has a certain amount of money stashed,
+the only constraint stopping you from robbing each of them is that adjacent houses have security systems connected and
+it will automatically contact the police if two adjacent houses were broken into on the same night.
+
+Given an integer array nums representing the amount of money of each house, return the maximum amount of money you can
+rob tonight without alerting the police.
+
+```plain
+Example 1:
+
+Input: nums = [1,2,3,1]
+Output: 4
+Explanation: Rob house 1 (money = 1) and then rob house 3 (money = 3).
+Total amount you can rob = 1 + 3 = 4.
+Example 2:
+
+Input: nums = [2,7,9,3,1]
+Output: 12
+Explanation: Rob house 1 (money = 2), rob house 3 (money = 9) and rob house 5 (money = 1).
+Total amount you can rob = 2 + 9 + 1 = 12.
+```
+
+## Related Topics
+
+- Array
+- Dynamic Programming

algorithms/dynamic_programming/house_robber/__init__.py

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+from typing import List
+
+
+def rob(nums: List[int]) -> int:
+    """Uses a top-down approach using Rolling Window technique where the idea is to only remember what is the maximum
+    gain at the next three houses from the current position."""
+    current, previous = 0, 0
+
+    for house in nums:
+        current, previous = max(previous + house, current), current
+
+    return current

algorithms/dynamic_programming/house_robber/test_house_robber.py

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+import unittest
+from . import rob
+
+
+class MyTestCase(unittest.TestCase):
+    def test_1(self):
+        """should return 4 for nums = [1,2,3,1]"""
+        nums = [1, 2, 3, 1]
+        expected = 4
+        actual = rob(nums)
+        self.assertEqual(expected, actual)
+
+    def test_2(self):
+        """should return 4 for nums = [2,7,9,3,1]"""
+        nums = [2, 7, 9, 3, 1]
+        expected = 12
+        actual = rob(nums)
+        self.assertEqual(expected, actual)
+
+    def test_3(self):
+        """should return 0 for nums = []"""
+        nums = []
+        expected = 0
+        actual = rob(nums)
+        self.assertEqual(expected, actual)
+
+    def test_4(self):
+        """should return 3 for nums = [3]"""
+        nums = [3]
+        expected = 3
+        actual = rob(nums)
+        self.assertEqual(expected, actual)
+
+    def test_5(self):
+        """should return 3 for nums = [3, 5]"""
+        nums = [3, 5]
+        expected = 5
+        actual = rob(nums)
+        self.assertEqual(expected, actual)
+
+
+if __name__ == '__main__':
+    unittest.main()