feat: ✨ Finish Iteration

Iteration/Recursion.cs

@@ -0,0 +1,35 @@
+namespace Iteration;
+
+public class Recursion
+{
+    public static bool IsAlphanum(string s, int i)
+    {
+        if (i >= s.Length)
+        {
+            return true;
+        }
+        else
+        {
+            if ((s[i] >= 'a' && s[i] <= 'z') || (s[i] >= 'A' && s[i] <= 'Z') || (s[i] >= '0' && s[i] <= '9'))
+            {
+                return IsAlphanum(s, i + 1);
+            }
+            else
+            {
+                return false;
+            }
+        }
+    }
+
+    public static string ReverseStr(string source, int lenght)
+    {
+        if (lenght == 0)
+        {
+            return "";
+        }
+        else
+        {
+            return source[lenght - 1] + ReverseStr(source, lenght - 1);
+        }
+    }
+}