Add example of adapter pattern in C++

cpp/patterns/adapter/main.cpp

@@ -0,0 +1,20 @@
+
+#include <iostream>
+
+#include "adapter.hpp"
+
+int main(const int argc, const char * argv[]) {
+  const int a = 5;
+  const int b = 10;
+  std::cout << "A = " << a << "\nB = " << b << std::endl;
+
+  // Testing target implementation
+  Add adder;
+  std::cout << "Adding a + b: " << adder.doMath(a, b) << std::endl;
+
+  // Testing RandomAddAdapter using RandomNumber as the adaptee
+  RandomNumber *adaptee = new RandomNumber(100);
+  RandomAddAdapter *adapter = new RandomAddAdapter(adaptee);
+  std::cout << "\nAdding a + b + RandomNumber: " << adapter->doMath(a, b)
+            << std::endl;
+}