added new exercices

Algorithms/IdCard/PostalCode.cs

@@ -0,0 +1,17 @@
+using System.Text.RegularExpressions;
+
+namespace Algorithms.IdCard;
+
+public class PostalCode
+{
+    private string postalCode;
+    public PostalCode(string postalCode)
+    {
+        this.postalCode = postalCode;
+    }
+
+    public bool IsValid(){
+        Regex rx = new Regex(@"^[A-Z]\d[A-Z] \d[A-Z]\d$");
+        return rx.Match(this.postalCode).Success;
+    }
+}