Easy

Question

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.

Example 1:

Input: prices = [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.
Note that buying on day 2 and selling on day 1 is not allowed because you must buy before you sell.

Example 2:

Input: prices = [7,6,4,3,1]
Output: 0
Explanation: In this case, no transactions are done and the max profit = 0.

Constraints:

• 1 <= prices.length <= 105
• 0 <= prices[i] <= 104

Hint

Solution

My Solution:

class Solution:
    def maxProfit(self, prices: List[int]) -> int:
        profit = 0
        buy = 0
        for sell in range(len(prices)):
            # if sell price is lower than buy price
            if prices[sell] < prices[buy]:
                buy = sell
            else:
                profit = max(profit, prices[sell]-prices[buy])
        return profit

Time Complexity: O(n)

Space Complexity: O(1)