Best Time to Buy and Sell Stock

The problem 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 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. 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 Brute force solution func maxProfit(_ prices: [Int]) -> Int { let n = prices.count var res = 0 for i in 0 ..< n { for j in i + 1 ..< n { let profit = prices[j] - prices[i] if profit > 0 { res = max(res, profit) } } } return res } Explanation We can start with a brute force solution and find a way to a more optimal solution as we go. By visualizing the problem using input from example 1 [7,1,5,3,6,4]: ...