refactor: refactor project structure

legacy/326 isPowerOfThree/C#/Program.cs

@@ -0,0 +1,21 @@
+public class Solution {
+    public bool IsPowerOfThree(int n) {
+        if(n <= 0)
+            return false;
+        if(n == 1)
+            return true;
+        if(n % 3 != 0)
+            return false;
+        return IsPowerOfThree(n/3);
+    }
+}
+
+class program{
+    static void Main(){
+        var Solution = new Solution();
+
+        Console.WriteLine(Solution.IsPowerOfThree(9));
+        Console.WriteLine(Solution.IsPowerOfThree(0));
+        Console.WriteLine(Solution.IsPowerOfThree(-1));
+    }
+}

legacy/326 isPowerOfThree/C#/isPowerOfThree.csproj

@@ -0,0 +1,10 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net8.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>