Best Time to Buy and Sell Stock

Best Time to Buy and Sell Stock

You are given an array prices where prices[i] is the price of a given stock on the i-th 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.

Examples

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: No transaction yields a positive profit, so the maximum profit is 0.

Example 3:

Input: prices = [2, 4, 1]
Output: 2
Explanation: Buy on day 1 (price = 2) and sell on day 2 (price = 4), profit = 4 - 2 = 2.

Constraints

• 1 <= prices.length <= 10^5
• 0 <= prices[i] <= 10^4

Expected Complexity

• Time: O(n)
• Space: O(1)