python: add problem 121 and unittest

Author: supercoderhawk

Python/sln_101_200/solution_121_130.py

@@ -0,0 +1,21 @@
+# -*- coding: utf-8 -*-
+from typing import List
+
+
+class Solution_121_130(object):
+    def maxProfit(self, prices: List[int]) -> int:
+        """
+        121
+        :param prices:
+        :return:
+        """
+        if len(prices) <= 1:
+            return 0
+        max_profit = prices[1] - prices[0]
+        lowest_profit = prices[0]
+        for price in prices[1:]:
+            if price < lowest_profit:
+                lowest_profit = price
+            if price - lowest_profit > max_profit:
+                max_profit = price-lowest_profit
+        return max_profit

Python/sln_101_200/test_solution_121_130.py

@@ -0,0 +1,12 @@
+# -*- coding: utf-8 -*-
+from unittest import TestCase
+from sln_101_200.solution_121_130 import Solution_121_130
+
+class Test_Solution_121_130(TestCase):
+    def setUp(self) -> None:
+        self.sln = Solution_121_130()
+
+    def test_maxProfit(self):
+        a = [7,1,5,3,6,4]
+        max_val = self.sln.maxProfit(a)
+        self.assertEqual(max_val, 5)