update(array) : buy sell stock'

Author: dhrubach

simple_array/e_buy_sell_stock_once.py

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+######################################################################
+# LeetCode Problem Number : 121
+# Difficulty Level : Easy
+# URL : https://leetcode.com/problems/best-time-to-buy-and-sell-stock/
+######################################################################
+from typing import List
+
+
+class BuySellStock:
+    def calculate(self, prices: List[int]) -> int:
+        max_profit, min_price_so_far = 0, prices[0]
+
+        for i in range(1, len(prices)):
+            max_profit_sell_today = prices[i] - min_price_so_far
+            max_profit = max(max_profit, max_profit_sell_today)
+            min_price_so_far = min(min_price_so_far, prices[i])
+
+        return max_profit

simple_array/h_buy_sell_stock_twice.py

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+###########################################################################
+# LeetCode Problem Number : 123
+# Difficulty Level : Hard
+# URL : https://leetcode.com/problems/best-time-to-buy-and-sell-stock-iii/
+##########################################################################
+from typing import List
+
+
+class BuySellStockTwice:
+    def calculate(self, prices: List[int]) -> int:
+        max_profit, min_price_so_far = 0, prices[0]
+        first_buy_sell = [0] * len(prices)
+
+        for i in range(1, len(prices)):
+            max_profit_sell_today = prices[i] - min_price_so_far
+            max_profit = max(max_profit, max_profit_sell_today)
+            min_price_so_far = min(min_price_so_far, prices[i])
+            first_buy_sell[i] = max_profit
+
+        max_sell_so_far = float("-inf")
+        for i, price in reversed(list(enumerate(prices[1:], 1))):
+            max_sell_so_far = max(max_sell_so_far, price)
+            max_profit = max(
+                max_profit, max_sell_so_far - price + first_buy_sell[i - 1]
+            )
+
+        return max_profit

simple_array/tests/e_buy_sell_stock_once_test.py

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+from simple_array.e_buy_sell_stock_once import BuySellStock
+
+
+class TestBuySellStock:
+    def test_max_profit(self):
+        bs = BuySellStock()
+
+        input = [310, 315, 275, 295, 260, 270, 290, 230, 255, 250]
+        result = bs.calculate(input)
+        assert result == 30
+
+    def test_decrease_price(self):
+        bs = BuySellStock()
+
+        input = [310, 300, 290, 280, 270]
+        result = bs.calculate(input)
+        assert result == 0

simple_array/tests/h_buy_sell_stock_twice_test.py

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+from simple_array.h_buy_sell_stock_twice import BuySellStockTwice
+
+
+class TestBuySellStockTwice:
+    def test_max_profit(self):
+        bs = BuySellStockTwice()
+
+        input = [12, 11, 13, 9, 12, 8, 14, 13, 15]
+        result = bs.calculate(input)
+        assert result == 10
+
+        input = [1, 2, 3, 4, 5]
+        result = bs.calculate(input)
+        assert result == 4
+
+    def test_decrease_price(self):
+        bs = BuySellStockTwice()
+
+        input = [7.6, 4, 3, 1]
+        result = bs.calculate(input)
+        assert result == 0