/*

I want to know how much money I could have made yesterday if I'd been trading Apple stocks all day.

​

So I grabbed Apple's stock prices from yesterday and put them in an array/list called stockPrices, where:

1. The indices are the time (in minutes) past trade opening time, which was 9:30am local time.

2. The values are the price (in US dollars) of one share of Apple stock at that time.

​

So if the stock cost $500 at 10:30am, that means stockPrices[60] = 500.

No "shorting" — you need to buy before you can sell. Also, you can't buy and sell in the same time step, at 

least 1 minute has to pass.

​

Problem 1: 

Write an efficient method that takes stockPrices and returns the best profit I could have made from one 

purchase and one sale of one share of Apple stock yesterday.

​

For example:

  int[] stockPrices = { 10, 7, 5, 8, 7, 11, 9 };

  // Returns 6 (buying for $5 and selling for $11)

  TradeOnce(stockPrices);

Problem 2:

Write an efficient method that takes stockPrices and returns the best profit I could have made from multiple

trades of one share of Apple stock yesterday.

​

For example:

  int[] stockPrices = { 10, 7, 5, 8, 7, 11, 9 };

  // Returns 7 (buying for $5 and selling for $8, buying for $7 and selling for $11)

  TradeMultiple(stockPrices);

*/

​

using System;

using System.Collections.Generic;

​

public class Program

{

    public static void Main()

    {

        int[] stockPrices = { 10, 7, 5, 8,7, 11, 9 };

        TradeOnce(stockPrices);

        TradeMultiple(stockPrices); 

    }

    public static void TradeOnce(int[] stockPrices)

    {

        var maxProfit = 0;

        // start and end prices

        var start = 0;

        var end = stockPrices.Length;

        //loop though prices

        for (var i=0; i<end; i++) {

            var currentPrice = stockPrices[i];

            // we need to compare against which price we buy and sell

            for(var j = i + 1; j <end; j++) {

                var newprice = stockPrices[j];

                if (currentPrice < newprice) {

                    var currentProfit = newprice -currentPrice;

                    if (currentProfit > maxProfit) {

                        maxProfit = currentProfit;                      

                    }                   

                }

            }

        }

        Console.WriteLine("If I trade once, maximum profit is: " + maxProfit);

        return;

    }

    public static void TradeMultiple(int[] stockPrices)

    {

        // int[] stockPrices = { 10, 7, 5, 8, 11, 9 };

        var maxProfit = 0;

        var end = stockPrices.Length;

        var minimum_price = 0;

        //loop though prices

        for (var i=0; i<end; i++) {

            var currentPrice = stockPrices[i];

            // we need to compare against which price we buy and sell

            //Will get the minimum value and compare against all elements

            minimum_price = stockPrices[0];

            minimum_price = Math.Min(stockPrices[0], stockPrices[i]) ;

            var profit = stockPrices[i] - minimum_price;

            //will check for profit 

            maxProfit = Math.Max(maxProfit, profit);

        }

        Console.WriteLine("If I trade multiple times, maximum profit is: " + maxProfit);

        return;

    }

}