LeetCode: Best Time to Buy and Sell Stock II https://leetcode.com/problems/best-time-to-buy-and-sell-stock-ii/

Please review for performance.


  Say you have an array for which the i-th element is the price of a
  given stock on day i.
  
  Design an algorithm to find the maximum profit. You may complete as
  many transactions as you like (i.e., buy one and sell one share of the
  stock multiple times).
  
  Note: You may not engage in multiple transactions at the same time
  (i.e., you must sell the stock before you buy again).

Example 1:

Input: [7,1,5,3,6,4]
Output: 7
Explanation: Buy on day 2 (price = 1) and sell on day 3 (price = 5), profit = 5-1 = 4.
             Then buy on day 4 (price = 3) and sell on day 5 (price = 6), profit = 6-3 = 3.
Example 2:

Input: [1,2,3,4,5]
Output: 4
Explanation: Buy on day 1 (price = 1) and sell on day 5 (price = 5), profit = 5-1 = 4.
             Note that you cannot buy on day 1, buy on day 2 and sell them later, as you are
             engaging multiple transactions at the same time. You must sell before buying again.
Example 3:

Input: [7,6,4,3,1]
Output: 0
Explanation: In this case, no transaction is done, i.e. max profit = 0.



using Microsoft.VisualStudio.TestTools.UnitTesting;

namespace ArrayQuestions
{
    /// &lt;summary&gt;
    /// https://leetcode.com/explore/featured/card/top-interview-questions-easy/92/array/564/
    /// &lt;/summary&gt;
    [TestClass]
    public class BestTimetoBuyandSellStockII
    {
        [TestMethod]
        public void AnswerIs7()
        {
            int[] prices = {7, 1, 5, 3, 6, 4};
            Assert.AreEqual(7, MaxProfit(prices));
        }

        public int MaxProfit(int[] prices)
        {
            int max = 0;
            for (int i = 0; i &lt; prices.Length-1; i++)
            {
                if (prices[i] &lt; prices[i + 1])
                {
                    max += prices[i + 1] - prices[i];
                }
            }
            return max;

        }
    }
}
Performance

Your solution is a single pass with time complexity \$O(n)\$. It's a small variation of the proposed solution. 

Conventions


use static when no instance state/operations are used
use a clear, non-abbreviated method name CalculateMaximumProfit
always guard against bad user input in public methods
prefer the use of var when the type is obvious when reading the code
prefer whitespace between operands and operators prices.Length - 1
clean up waisted whitespace (in this case, after the return statement)


applied to your code:

 public static int CalculateMaximumProfit(int[] prices)
 {
     prices = prices ?? throw new ArgumentNullException(nameof(prices));
     var max = 0;
     for (var i = 0; i &lt; prices.Length - 1; i++)
     {
         if (prices[i] &lt; prices[i + 1])
         {
             max += prices[i + 1] - prices[i];
         }
     }
     return max;
 }