add possibility to print a set to a string

Assignment_2/lib/Set.cpp

@@ -1,6 +1,9 @@
 #include "Set.h"
 #include "Node.h"
 
+#include <iostream>
+#include<sstream>
+
 Set::Set(std::string _name){
     name = _name;
     first = Node::Dummy();
@@ -11,3 +14,13 @@ bool Set::add(int element) { return false; }
 bool Set::rmv(int element) { return false; }
 bool Set::ctn(int element) { return false; }
 std::string Set::get_name() { return name; }
+
+std::string Set::print_set(){
+    Node* c = this->first->next;
+    std::stringstream ss;
+    while (!c->is_dummy()) {
+        ss << c->get_data() << " ";
+        c = c->next;
+    }
+    return ss.str();
+}