diff --git a/week0004/HaiHa/cpp/PrintOutDuplicateInfo.cpp b/week0004/HaiHa/cpp/PrintOutDuplicateInfo.cpp
new file mode 100644
index 0000000..e33a009
--- /dev/null
+++ b/week0004/HaiHa/cpp/PrintOutDuplicateInfo.cpp
@@ -0,0 +1,101 @@
+#include <algorithm>
+#include <fstream>
+#include <iostream>
+#include <set>
+#include <regex>
+
+class Participant
+{
+
+public:
+  Participant (std::string firstName, std::string lastName, std::string email) :
+    m_firstName(firstName),
+    m_lastName(lastName),
+    m_email(email)
+    {
+    }
+
+  bool operator< (const Participant &rhs) const
+  {
+    if (m_firstName != rhs.m_firstName)
+      return (m_firstName < rhs.m_firstName);
+    else if (m_lastName != rhs.m_lastName)
+      return (m_lastName < rhs.m_lastName);
+    else
+      return (m_email < rhs.m_email);
+  }
+
+  friend std::ostream & operator<<(std::ostream &out, Participant input)
+  {
+    return out << input.m_firstName << " " << input.m_lastName << " <" <<
+      input.m_email << ">";
+  }
+
+private:
+  std::string m_firstName;
+  std::string m_lastName;
+  std::string m_email;
+};
+
+typedef std::set<Participant> SortedParticipantList;
+
+//------------------------------------------------------------------------------
+
+/**Parse a line and add it to the participant list**/
+void ParseParticipantInformation(const std::string &line, SortedParticipantList
+    &ParticipantList, const std::regex &pattern)
+{
+  std::smatch match;
+
+  if ((std::regex_match(line, match,pattern)) && (match.size() == 4))
+    ParticipantList.emplace(match[1], match[2], match[3]);
+}
+
+//------------------------------------------------------------------------------
+
+/** Get participant list from input file**/
+void GetParticipantListFromFile(const std::string &fileName, SortedParticipantList &ParticipantList)
+{
+  std::ifstream inputStream(fileName);
+  std::string line;
+
+  if(!inputStream)
+  {
+    std::cout << "Cannot open input file.\n";
+  }
+  else
+  {
+    //Ignore the first line as title.
+    std::getline(inputStream, line);
+
+    const std::regex pattern("(\\w+),(\\w++),([A-z0-9._%+-]+@\\w+\\.\\w+)");
+
+    while (std::getline(inputStream, line))
+      ParseParticipantInformation(line, ParticipantList, pattern);
+
+    inputStream.close();
+  }
+}
+
+//------------------------------------------------------------------------------
+
+void PrintOutIntersectionForSets(const SortedParticipantList &list1, const SortedParticipantList &list2)
+{
+  std::set_intersection(list1.begin(), list1.end(), list2.begin(), list2.end(),
+    std::ostream_iterator<Participant>(std::cout, "\n"));
+}
+
+
+int main(int argc, char *argv[])
+{
+  SortedParticipantList eventA;
+  SortedParticipantList eventB;
+
+  // Get file names from command line
+  GetParticipantListFromFile(argv[1], eventA);
+  GetParticipantListFromFile(argv[2], eventB);
+
+  PrintOutIntersectionForSets(eventA, eventB);
+
+  return 0;
+}