Add alternative solution to code-quality/c33010.md

Author: michaelwoerister

docs/code-quality/c33010.md

@@ -71,6 +71,31 @@ void foo(Index idx, PFN(&functions)[5])
 }
 ```
 
+Alternatively, the issue can be fixed by choosing an underlying type for `Index` that is unsigned. Because an unsigned value is always positive, it is sufficient to only check the upper bound.
+
+```cpp
+typedef void (*PFN)();
+
+enum class Index : unsigned int
+{
+    Zero,
+    One,
+    Two,
+    Three,
+    Max
+};
+
+void foo(Index idx, PFN(&functions)[5])
+{
+    if (idx > Index::Max)
+        return;
+
+    auto pfn = functions[static_cast<unsigned int>(idx)];
+    if (pfn != nullptr)
+        (*pfn)();
+}
+```
+
 ## See also
 
 [C33011](./c33011.md)