Day3. Start Algorithm

121. Best Time to Buy and Sell Stock/121. Best Time to Buy and Sell Stock.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+    <RootNamespace>_121._Best_Time_to_Buy_and_Sell_Stock</RootNamespace>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>

121. Best Time to Buy and Sell Stock/Program.cs

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+namespace _121._Best_Time_to_Buy_and_Sell_Stock
+{
+    internal class Program
+    {
+        static void Main(string[] args)
+        {
+            Console.WriteLine(new Solution().MaxProfit(new int[] { 7, 1, 5, 3, 6, 4 }));
+        }
+    }
+}

121. Best Time to Buy and Sell Stock/Solution.cs

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+namespace _121._Best_Time_to_Buy_and_Sell_Stock;
+
+public class Solution
+{
+    public int MaxProfit(int[] prices)
+    {
+        int min = prices[0];
+        int max = prices[0];
+        bool hasMax = false;
+        int res = 0;
+        foreach (int price in prices)
+        {
+            if (price > max || hasMax == false)
+            {
+                max = price;
+                hasMax = true;
+                res = Math.Max(max - min, res);
+            }
+            if (price < min)
+            {
+                min = price;
+                hasMax = false;
+            }
+        }
+        return res > 0 ? res : 0;
+    }
+}