Best Time to Buy and Sell StockEdit

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.

Solution:

  • Time: O(n)
  • Space: O(1)
int MaxProfit(int[] prices)
{
    var minPrice = int.MaxValue;
    var maxProfit = 0;

    for (var i = 0; i < prices.Length; i++)
    {
        if (prices[i] < minPrice)
        {
            minPrice = prices[i];
        }

        var profit = prices[i] - minPrice;
        if (profit > maxProfit)
        {
            maxProfit = profit;
        }
    }

    return maxProfit;
}

See also