Question

C++ Data Structure

Write a program to read a list of students from a file and create a list. The program should use a linked list for implementation. Each node in the linked list should have the student’s name, a pointer to the next student, and a pointer to a linked list of scores. There may be up to four scores for each student.

Answer 1

Answer summary :

Before writing the code let me explain it briefly. Here in this question we have to construct Linked list within a Linked List. So according to the question, initially we construct a Linked list of the students names. Each time when we create a node in the linked list of student names we initialise the head node for the scores of that student too. Then we run a loop to obtain the scores of the student and then insert in the scores linked list of each student node.

Each line in the input file is considered to be in the following format:

student_name score1 score2 score3 score4 . . . scoreN

student_name score1 score2 score3 score4 . . . scoreN

The proper explanation of the code is given within the comments in code

Input file (Input.txt) :

student1 1 2 3 4
student2 5 6 7 8
student3 9 10 11 12

C++ code:

   #include <bits/stdc++.h>
   #include <fstream>
   // The Input file name is given here
   std::ifstream file("input.txt");
   using namespace std;

   // The Node class for each score of the student
   class ScoreNode
   {
   public:
   string score;
   ScoreNode* next;
   };

   // The Node class for each Student Node
   class StudentNode
   {
   public:
   string name;
   ScoreNode* scores; // Pointer to the Linked List of Scores
   StudentNode* next;
   };

   // Function which Inserts the students name in the linked List
   void pushStudent(StudentNode** head_ref, string new_name)
   {
   StudentNode* new_Studentnode = new StudentNode();
   new_Studentnode->name = new_name;
   new_Studentnode->scores = NULL; //Intiallizes the Score Linked List for each student
   new_Studentnode->next = (*head_ref);
   (*head_ref) = new_Studentnode;
   }

   // Function to insert the score of each students in their respective linked lists
   void pushScore(ScoreNode** head_ref, string new_score)
   {
   ScoreNode* new_Scorenode = new ScoreNode();
   new_Scorenode->score = new_score;
   new_Scorenode->next = (*head_ref);
   (*head_ref) = new_Scorenode;
   }

   int main() {
       StudentNode* head = NULL;
       // First we have to Open the file
       if (file.is_open()) {
       // Now read Line by line
   std::string line;
   while (getline(file, line)) {
       // Each line contains the student Info
       string StudentInfo = line.c_str();
       // Split the info using stringstream
       istringstream ss(StudentInfo);
       // Collect the name of the student
       string name;
       ss >> name;    
       // Insert the name in the linked list
           pushStudent(&head,name);
           // Now collect all the scores of the student
           while(ss) {
       string score;
       ss >> score;
       // Push the collected score to the linked list of that student
       if(score!="")
               pushScore(&head->scores,score);
   // While there is more to read
       }
       cout<<endl;
       }

       }
       // Now the output
       // Each line displays the each students name and their corresponding linked list of scores
       cout<<"List of Students"<<endl;
       StudentNode* node = head;
       while (node != NULL)
       {    
       cout<<node->name<<" ";
       cout<<"Linked List of Scores : ";
       ScoreNode* p = node->scores;
           while (p != NULL)
           {
           cout<<p->score<<"->";
           p = p->next;
           }
           cout<<endl;
       node = node->next;
       }
   return 0;
   }

output :

List of Students
student3 Linked List of Scores : 12->11->10->9->
student2 Linked List of Scores : 8->7->6->5->
student1 Linked List of Scores : 4->3->2->1->