Linked list program for student average - c

Question

I am new to C programming especially linked list. Can someone please help me with my code? When I compile the program there is no error but when I try to run the program its output is wrong. I don't know if the storing is wrong or the printing.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
/* self-referential structure */
struct listNode {
char name[80];
char subject[80]; /* each listNode contains a character */
float unit;
float grade;
struct listNode *nextPtr; /* pointer to next node */
}; /* end structure listNode */
typedef struct listNode ListNode; /* synonym for struct listNode */
typedef ListNode *ListNodePtr; /* synonym for ListNode* */
/* prototypes */
void insert(ListNodePtr *sPtr, char SUB[80], float grade, float unit, char NAME[80]);
int isEmpty(ListNodePtr sPtr);
void printList(ListNodePtr currentPtr, ListNodePtr *sPtr);
void instructions(void);
int main(void)
{
ListNodePtr startPtr = NULL; /* initially there are no nodes */
int choice; /* user's choice */
float grades, units;
char subn[80], stdn[80];
int i, j, std = 0, sub = 0;
instructions(); /* display the menu */
printf("? ");
scanf("%d", &choice);
/* loop while user does not choose 3 */
while (choice != 3) {
switch (choice) {
case 1: /* input data */
printf("Number of Students: (at least 5 students)\n");
scanf("%d", &std);
for (i = 0; i < std; i++) {
printf("\nStudent name: ");
scanf("%s", &stdn);
printf("How many subjects?\n");
scanf("%d", &sub);
for (j = 0; j < sub; j++) {
printf("\nSub­ject: ");
scanf("%s", &subn);
printf("Units­: ");
scanf("%f", &units);
printf("Final­ Grade: ");
scanf("%f", &grades);
insert(&startPtr, subn, grades, units, stdn);
}
}
break;
case 2:
printList(startPtr, &startPtr);
break;
default:
printf("Invalid choice.\n\n");
instructions();
break;
} /* end switch */
printf("\n\n? ");
scanf("%d", &choice);
} /* end while */
printf("End of run.\n");
return 0; /* indicates successful termination */
} /* end main */
/* display program instructions to user */
void instructions(void)
{
printf("Enter your choice:\n"
" 1 to Input Student Data.\n"
" 2 to Display Student Data.\n"
" 3 to end.\n");
} /* end function instructions */
/* for series */
void insert(ListNodePtr *sPtr, char SUB[80], float grade, float unit, char NAME[80])
{
ListNodePtr newPtr; /* pointer to new node */
ListNodePtr previousPtr; /* pointer to previous node in list */
ListNodePtr currentPtr; /* pointer to current node in list */
newPtr = malloc(sizeof(ListNode)); /* create node */
if (newPtr != NULL) { /* is space available */
strcpy(newPtr->na­me, NAME);
strcpy(newPtr->subject, SUB); /* place value in node */
newPtr->grade = grade;
newPtr->unit = unit;
newPtr->nextPtr = NULL; /* node does not link to another node */
previousPtr = NULL;
currentPtr = *sPtr;
/* insert new node at beginning of list */
if (previousPtr == NULL) {
newPtr->nextPtr = *sPtr;
*sPtr = newPtr;
} /* end if */
else { /* insert new node between previousPtr and currentPtr */
previousPtr->nex­tPtr = newPtr;
newPtr->nextPtr = currentPtr;
} /* end else */
} /* end if */
else {
printf("Student data not inserted. No memory available.\n");
} /* end else */
} /* end function insert */
int isEmpty(ListNodePtr sPtr)
{
return sPtr == NULL;
} /* end function isEmpty */
/* Print the list */
void printList(ListNodePtr currentPtr, ListNodePtr *sPtr)
{
float total = 0.00, total2 = 0.00;
/* if list is empty */
if (currentPtr == NULL) {
printf("List is empty.\n\n");
} /* end if */
else {
printf("\n");
printf("%-20s\t%s\­t%s\n", "Subject", "Units", "Final Grade");
/* while not the end of the list */
while (currentPtr != NULL) {
printf("Student­ Name: %s\n", currentPtr->name);
printf("%-20s\t%.2f\t%.2f\n­", currentPtr->subject, ­ currentPtr->unit, currentPtr->grade);
total += currentPtr->unit;
total2 += currentPtr->unit*cur­rentPtr->grade;
currentPtr = currentPtr->nextPtr;
} /* end while */
printf("\nWeight:­ %.2f", total2 / total);
printf("\n///////­/////////////////////­/////////////////////­///");
} /* end else */
} /* end function printList */

Answer 1

Heading
Hi,
I have not looked thoroughly in the code . But , in a quick look I spotted the following basic problem
nextPtr should be a pointer, you are creating an instance and copying the contents of the next structure. This is not efficient.
I will declare it as below
struct listNode *nextPtr; / pointer to next node */
Again , I will change the followingtypedef ListNode ListNodePtr;
typedef ListNode ListNodePtr;
to
typedef ListNode *ListNodePtr;
Try to restructure your code with this, and see how it goes. If not helping, I can have a detailed look in the evening.