[C++/en] feat: update iterator to use auto

c++.md

@@ -908,12 +908,20 @@ for (int i = 0; i < my_vector.size(); i++) {
     std::cout << my_vector[i] << '\n'; // for accessing a vector's element we can use the operator []
 }
 
-// or using an iterator:
+// or using an iterator (old fashion):
 vector<string>::iterator it; // initialize the iterator for vector
 for (it = my_vector.begin(); it != my_vector.end(); ++it) {
     std::cout << *it  << '\n';
 }
 
+// modern way of using an iterator
+for (auto it = my_vector.begin(); it != my_vector.end(); ++it) {
+    std::cout << *it << '\n';
+}
+// (elegantly) or using the reference of the original object + using `auto` syntax 
+    for (auto& it : vec) {
+        std::cout << it << std::endl;
+    }
 // Set
 // Sets are containers that store unique elements following a specific order.
 // Set is a very useful container to store unique values in sorted order