Question

Write down a C program which will create a list (simple linear linked list) of nodes. Each node consists of two fields. The first field is a pointer to a structure that contains a student id (integer) and a grade-point average (float). The second field is a link. The data are to be read from a text file. Your program should read a file of 10 students (with student id and grade point average) and test the function you wrote (by printing student’s information on screen). (Please comment the codes)

Answer 1

//C program

#include<stdio.h>
#include<stdlib.h>

//structure student
struct student{
   int id;
   float grade;
};

//Node structure
struct Node{
   struct student* st;
   struct Node*next;
};

//adding new node to link list
struct Node* addNode(struct Node * head , int id , float grade){
   //declaring and memory allocation to struct student pointer
   struct student * newSt = (struct student*) malloc(sizeof(struct student));
   newSt->id = id;
   newSt->grade = grade;
  
   //declaring and memory allocation to struct Node pointer
   struct Node* newNode = (struct Node*) malloc(sizeof(struct Node));
   newNode->st = newSt;
   newNode->next = NULL;
  
   //if list is empty
   if(head==NULL)return newNode;
  
   struct Node*current = head;
  
   while(current->next)current = current->next;
  
   current->next = newNode;
  
   return head;
}

//funcion to display linkedlist
void display(struct Node*head){
   while(head){
       printf("ID : %d\n",head->st->id);
       printf("Grade : %.2f\n\n",head->st->grade);
       head = head->next;
   }
}

//main driver function
int main(){
   //variable declaration
   int id;
   float grade;
   struct Node* head = NULL;
//opening file
FILE* fp = fopen("input.txt", "r"); // read mode
//if file does not opened
if (fp == NULL)
{
printf("Error while opening the file.\n");
return 0;
}
//reading data from file
while (!feof (fp))
{
fscanf (fp, "%d", &id);
fscanf (fp, "%f", &grade);
   //adding new data to existing linkedlist as a ne node
   head = addNode(head,id,grade);
}
//displaying linkedlist
display(head);
//closing file
fclose (fp);
return 0;
}