6.19 Lab: Doubly-Linked List (Insert & Display)

04-dl-lists/StudentList.cpp

@@ -5,6 +5,7 @@
 // IDE: CLion
 #include <iostream>         // For cout  and NULL
 #include "StudentList.h"
+
 using namespace std;
 
 // **************************************************
@@ -15,14 +16,13 @@ using namespace std;
 //      by making sure that all links can be safely dereferenced and that every list
 //      (even one that contains no data elements) always has a "first" node.
 // **************************************************
-StudentList::StudentList()
-{
+StudentList::StudentList() {
     head = new ListNode; // head points to the sentinel node
 
     head->stu.gpa = -1;
     head->stu.name = "";
     head->forw = head;
-    /* Write your code here */
+    head->back = head;
     count = 0;
 }
 
@@ -31,16 +31,14 @@ StudentList::StudentList()
 // stored in each node of the linked list
 // pointed to by head. from A to Z
 // **************************************************
-void StudentList::displayListForw() const
-{
+void StudentList::displayListForw() const {
     ListNode *pCur;  // To move through the list
 
     // Position pCur: skip the head of the list.
     pCur = head->forw;
 
     // While pCur points to a node, traverse the list.
-    while (pCur != head)
-    {
+    while (pCur != head) {
         // Display the value in this node.
         cout << pCur->stu.gpa << " " << pCur->stu.name << endl;
 
@@ -49,24 +47,35 @@ void StudentList::displayListForw() const
     }
     cout << endl;
 }
+
 // **************************************************
-// display list forwards: shows the value
+// display list backwards: shows the value
 // stored in each node of the linked list
 // pointed to by head, from Z to A
 // **************************************************
+void StudentList::displayListBack() const {
+    ListNode *pCur;  // To move through the list
 
-void StudentList::displayListBack() const
-{
-    /* Write your code here */
+    // Position pCur: skip the head of the list.
+    pCur = head->back;
+
+    // While pCur points to a node, traverse the list.
+    while (pCur != head) {
+        // Display the value in this node.
+        cout << pCur->stu.gpa << " " << pCur->stu.name << endl;
+
+        // Move to the next node.
+        pCur = pCur->back;
+    }
 
     cout << endl;
 }
+
 // **************************************************
 // The insertNode function inserts a node with
 // stu copied to its value member.
 // **************************************************
-void StudentList::insertNode(Student dataIn)
-{
+void StudentList::insertNode(Student dataIn) {
     ListNode *newNode;  // A new node
     ListNode *pCur;     // To traverse the list
 
@@ -78,8 +87,7 @@ void StudentList::insertNode(Student dataIn)
     pCur = head->forw;
 
     // Find location: skip all nodes whose name is less than dataIn's name
-    while (pCur != head && pCur->stu.name < dataIn.name)
-    {
+    while (pCur != head && pCur->stu.name < dataIn.name) {
         pCur = pCur->forw;
     }
 
@@ -88,7 +96,8 @@ void StudentList::insertNode(Student dataIn)
     pPre->forw = newNode;
     newNode->forw = pCur;
 
-     /* Write your code here */
+    pCur->back = newNode;
+    newNode->back = pPre;
 
     // Update the counter
     count++;
@@ -98,7 +107,6 @@ void StudentList::insertNode(Student dataIn)
 // Destructor                                      *
 // This function deletes every node in the list.   *
 // **************************************************
-StudentList::~StudentList()
-{
+StudentList::~StudentList() {
 
 }

04-dl-lists/StudentList.h

@@ -9,18 +9,15 @@
 
 #include <string>
 
-struct Student
-{
+struct Student {
     double gpa;
     std::string name;
 };
 
-class StudentList
-{
+class StudentList {
 private:
     // Declare a structure for the list
-    struct ListNode
-    {
+    struct ListNode {
         Student stu;     // The value in this node
         ListNode *forw;  // To point to the next node
         ListNode *back;  // To point to the previous node
@@ -32,14 +29,18 @@ private:
 
 public:
     StudentList();  // Constructor
-   ~StudentList();   // Destructor
+    ~StudentList();   // Destructor
 
     // Linked list operations
-    int getCount() const {return count;}
+    int getCount() const { return count; }
+
     void insertNode(Student);
+
     //bool deleteNode(double);
     //void searchList() const;
     void displayListForw() const;
+
     void displayListBack() const;
 };
+
 #endif

04-dl-lists/main.cpp

@@ -27,8 +27,7 @@ using namespace std;
 
 void buildList(StudentList &);
 
-int main()
-{
+int main() {
     // Define a StudentList object
     StudentList list;
 
@@ -38,8 +37,7 @@ int main()
     string answer;
     cout << "Insert [Y/N]? ";
     getline(cin, answer);
-    if (answer == "Y" || answer == "y")
-    {
+    if (answer == "Y" || answer == "y") {
         Student s;
         cout << "Enter gpa then enter name:" << endl;
         cin >> s.gpa >> s.name;
@@ -48,7 +46,7 @@ int main()
     }
     cout << endl;
     list.displayListForw();
-    /* Write your code here: display the list from Z to A */
+    list.displayListBack();
     return 0;
 }
 
@@ -59,19 +57,17 @@ It calls the insertNode() function that inserts the new data at the right locati
 An input line contains the gpa of a student follow by its name (assume it is a single word name)
 To stop reading enter "#"
 ************************************************** */
-void buildList(StudentList &list)
-{
-   string line;
-   getline(cin, line);
-   while (line != "#")
-   {
-      stringstream temp(line); // create a stringstream named temp with data from line
-      Student newStu;
-      temp >> newStu.gpa;  // read gpa from temp
-      temp >> newStu.name; // read name from temp
-      list.insertNode(newStu);
-      getline(cin, line);
-   }
+void buildList(StudentList &list) {
+    string line;
+    getline(cin, line);
+    while (line != "#") {
+        stringstream temp(line); // create a stringstream named temp with data from line
+        Student newStu;
+        temp >> newStu.gpa;  // read gpa from temp
+        temp >> newStu.name; // read name from temp
+        list.insertNode(newStu);
+        getline(cin, line);
+    }
 
 }