diff --git a/shared_ptr.cpp b/shared_ptr.cpp
index 49f7273..5d897fa 100644
--- a/shared_ptr.cpp
+++ b/shared_ptr.cpp
@@ -1,5 +1,6 @@
 #include <cassert>
 #include <memory>
+#include <vector>
 
 // From Wikipedia.
 
@@ -21,6 +22,24 @@ void shared_ptr() {
   assert(p1.use_count() == 0);
 }
 
+void shared_ptr_container() {
+  std::shared_ptr<int> p1(new int(5));
+  std::shared_ptr<int> p2 = p1; // Both now own the memory.
+  assert(p1.use_count() == 2);
+
+  std::vector<std::shared_ptr<int>> v;
+  v.push_back(p1);
+  v.push_back(p1);
+  assert(p1.use_count() == 4);
+  p2.reset();
+  assert(p1.use_count() == 3);
+  assert(p2.use_count() == 0);
+
+  v.pop_back();
+  v.pop_back();
+  assert(p1.use_count() == 1);
+}
+
 void weak_ptr() {
   std::shared_ptr<int> p1(new int(5));
   std::weak_ptr<int> wp1 = p1; // p1 owns the memory.
@@ -50,5 +69,6 @@ void weak_ptr() {
 
 int main() {
   shared_ptr();
+  shared_ptr_container();
   weak_ptr();
 }