adding the iterator exercise code

lectures/10_linked_lists/README.md

@@ -140,6 +140,36 @@ itr++;
 assert (*itr == 100); // might seem ok... but rewrite the code to avoid this!
 ```
 
+### Exercise
+
+What is the output of this program?
+
+#include <list>
+#include <iostream>
+
+```cpp
+int main(){
+
+	std::list<int> lst;
+	lst.push_back(150);
+	lst.push_back(250);
+	lst.push_back(350);
+	lst.push_back(450);
+	
+	std::list<int>::iterator itr;
+	itr = lst.begin();
+	++itr;
+	*itr += 5;
+
+	std::list<int>::iterator itr2 = lst.begin();
+	while(itr2 != lst.end()){
+		std::cout << *itr2 << std::endl;
+		itr2++;
+	}
+	
+}
+```
+
 ## 10.3 Working towards our own version of the STL list
 
 - Our discussion of how the STL list&lt;T&gt; is implemented has been intuitive: it is a “chain” of objects.