Solution added.

Author: 149ps

30 Days September Challange/Week 3/4. Best Time to Buy and Sell Stock/solution.py

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+"""
+Say you have an array for which the ith element is the price of a given stock on day i.
+
+If you were only permitted to complete at most one transaction (i.e., buy one and sell one share of the stock), design an algorithm to find the maximum profit.
+
+Note that you cannot sell a stock before you buy one.
+
+Example 1:
+
+Input: [7,1,5,3,6,4]
+Output: 5
+Explanation: Buy on day 2 (price = 1) and sell on day 5 (price = 6), profit = 6-1 = 5.
+             Not 7-1 = 6, as selling price needs to be larger than buying price.
+Example 2:
+
+Input: [7,6,4,3,1]
+Output: 0
+Explanation: In this case, no transaction is done, i.e. max profit = 0.
+"""
+class Solution:
+    def maxProfit(self, prices: List[int]) -> int:
+        buy,profit = sys.maxsize,-sys.maxsize-1
+        for price in prices:
+            if price <= buy:
+                buy = price
+            else:
+                profit = max(profit,price-buy)
+        return profit if profit > 0 else 0