adding erase example

lectures/09_iterators_linked_lists/README.md

@@ -415,6 +415,34 @@ p = s.erase(p);
 Even though the erase function has the same syntax for vectors and for list, the vector version is O(n), whereas
 the list version is O(1). Play this [animation](https://jidongxiao.github.io/CSCI1200-DataStructures/animations/lists/iterator/index.html) to see why.
 
+Here is an [example program](list_erase.cpp) demonstrating the usage of safely erasing elements from an std::list while iterating over it.
+
+```cpp
+#include <iostream>
+#include <list>
+
+int main() {
+    std::list<int> numbers = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
+
+    // iterate over the list and remove even numbers
+    for (std::list<int>::iterator it = numbers.begin(); it != numbers.end(); ) {
+        if (*it % 2 == 0) {  // if the element is even
+            it = numbers.erase(it);  // erase returns the next valid iterator
+        } else {
+            ++it;  // move to the next element
+        }
+    }
+
+    // print the modified list
+    // range based for loop: all STL containers that provide begin() and end() member functions support range-based for loops (introduced in C++11).
+    for (int num : numbers) {
+        std::cout << num << " ";
+    }
+    std::cout << std::endl;
+    return 0;
+}
+```
+
 ## 9.10 Insert
 
 - Similarly, there is an insert function for STL lists that takes an iterator and a value and adds a link in the

lectures/09_iterators_linked_lists/list_erase.cpp

@@ -0,0 +1,23 @@
+#include <iostream>
+#include <list>
+
+int main() {
+    std::list<int> numbers = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
+
+    // iterate over the list and remove even numbers
+    for (std::list<int>::iterator it = numbers.begin(); it != numbers.end(); ) {
+        if (*it % 2 == 0) {  // if the element is even
+            it = numbers.erase(it);  // erase returns the next valid iterator
+        } else {
+            ++it;  // move to the next element
+        }
+    }
+
+    // print the modified list
+    // range based for loop: all STL containers that provide begin() and end() member functions support range-based for loops (introduced in C++11).
+    for (int num : numbers) {
+        std::cout << num << " ";
+    }
+    std::cout << std::endl;
+    return 0;
+}