new files to code-along with ll2 and ll4

Author: kascrizzi

datareps2/ll1.cc

@@ -1,4 +1,5 @@
 #include "ll.hh"
+#include <cassert>
 
 node* head = nullptr;
 

datareps2/ll2.cc

@@ -0,0 +1,37 @@
+#include "ll.hh"
+#include <cassert>
+
+node* head = nullptr;
+
+// Adds n to the end of the list whose head is head. 
+// Sets n->next and n->prev to the proper values. 
+// Assumes that n is a live node and not already a member of the list.
+void append(node* n) {
+    (void) n; // Placeholder to avoid compiler warnings. Replace with your code!
+}
+
+// representation checker
+void check_list() {
+    node* prev = nullptr;
+    node* trav = head;
+    while (trav) {
+        assert(trav->prev == prev);
+        prev = trav;
+        trav = trav->next;
+    }
+}
+
+int main() {
+    // Code to test 'append'
+	check_list();
+
+    node N1 = {1, nullptr, nullptr};
+    append(&N1);
+    check_list();
+    assert(head != nullptr);
+
+    node N2 = {2, nullptr, nullptr};
+    append(&N2);
+    check_list();
+    assert(head != nullptr);
+}

datareps2/ll4.cc

@@ -0,0 +1,65 @@
+#include "ll.hh"
+#include <cassert>
+
+node* head = nullptr;
+
+// Removes n from the list. 
+// Assumes that n is a live object and a member of the list.
+// Upon return, n is still a live object, but no longer a member of the list.
+void erase(node* n) {
+    (void) n; // Placeholder to avoid compiler warnings. Replace with your code!
+}
+
+// Adds n to the end of the list whose head is head. 
+// Sets n->next and n->prev to the proper values. 
+// Assumes that n is a live node and not already a member of the list.
+void append(node* n) {
+    node* prev = nullptr;
+    node* trav = head;
+    while (trav) {
+        prev = trav;
+        trav = trav->next;
+    }
+    n->prev = prev;
+    n->next = nullptr;
+    if (prev) {
+        prev->next = n;
+    } else {
+        head = n;
+    }
+}
+
+// representation checker
+void check_list() {
+    node* prev = nullptr;
+    node* trav = head;
+    while (trav) {
+        assert(trav->prev == prev);
+        prev = trav;
+        trav = trav->next;
+    }
+}
+
+int main() {
+    // Code to test 'erase'
+	check_list();
+
+    node N1 = {1, nullptr, nullptr};
+    node N2 = {2, nullptr, nullptr};
+    node N3 = {3, nullptr, nullptr};
+    append(&N1);
+    append(&N2);
+    append(&N3);
+    check_list();
+
+    erase(&N2);
+    check_list();
+
+    erase(&N3);
+    check_list();
+
+    erase(&N1);
+    check_list();
+
+    assert(head == nullptr);
+}

datareps2/ll6.cc

@@ -1,4 +1,5 @@
 #include "ll.hh"
+#include <cassert>
 
 node* head = nullptr;