D. J.:

- Added leetcode problem and solution for 121 Best Time to Buy and Sell Stock

Author: nobodyPerfecZ

README.md

@@ -8,6 +8,7 @@ This repository contains awesome LeetCode problems and solutions written in Pyth
 - [27 Remove Element](https://leetcode.com/problems/remove-element/description/)
 - [80 Remove Duplicates from Sorted Array II](https://leetcode.com/problems/remove-duplicates-from-sorted-array-ii/description/)
 - [88 Merge Sorted Array](https://leetcode.com/problems/merge-sorted-array/description/)
+- [121 Best Time to Buy and Sell Stock](https://leetcode.com/problems/best-time-to-buy-and-sell-stock/description/)
 - [169 Majority Element](https://leetcode.com/problems/majority-element/description/)
 
 ## Development 🔧

awesome_python_leetcode/_121_best_time_to_buy_and_sell_stocks.py

@@ -0,0 +1,23 @@
+from typing import List
+
+
+class Solution:
+    def maxProfit(self, prices: List[int]) -> int:
+        """
+        You are given an array prices where prices[i] is the price of a given stock on the ith day.
+
+        You want to maximize your profit by choosing a single day to buy one stock and choosing a different day in the future to sell that stock.
+
+        Return the maximum profit you can achieve from this transaction. If you cannot achieve any profit, return 0.
+        """
+        left, right, best_profit = 0, 1, 0
+        while right < len(prices):
+            if prices[left] > prices[right]:
+                left = right
+                right += 1
+            else:
+                profit = prices[right] - prices[left]
+                if profit > best_profit:
+                    best_profit = profit
+                right += 1
+        return best_profit

tests/test_121_best_time_to_buy_and_sell_stocks.py

@@ -0,0 +1,17 @@
+from typing import List
+
+import pytest
+
+from awesome_python_leetcode._121_best_time_to_buy_and_sell_stocks import Solution
+
+
+@pytest.mark.parametrize(
+    argnames=["prices", "expected"],
+    argvalues=[
+        ([7, 1, 5, 3, 6, 4], 5),
+        ([7, 6, 4, 3, 1], 0),
+    ],
+)
+def test_func(prices: List[int], expected: int):
+    max_profit = Solution().maxProfit(prices)
+    assert max_profit == expected