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

#define MAX_STR  32


typedef struct {
  char   name[MAX_STR];
  char   major[MAX_STR];
} StudentType;


typedef struct Node {
  StudentType  *data;
  struct Node  *next;
} NodeType;


void createStudent(char*, char*, StudentType**);
void createNode(NodeType**, StudentType*);
void printStudent(StudentType*);
void freeList(NodeType*);


int main() {
  NodeType    *ourClassroom = NULL;
  NodeType    *currNode = NULL;
  StudentType *currStudent;
  char         str1[MAX_STR];
  char         str2[MAX_STR];

  printf("\nEnter student names and their majors (use -1 when done): ");
  while(1) {
    printf("\nEnter name: ");
    scanf("%s", str1);
    if (strcmp(str1, "-1") == 0)
      break;
    printf("Enter major: ");
    scanf("%s", str2);

    createStudent(str1, str2, &currStudent);
    createNode(&currNode, currStudent);
    
    currNode->next = ourClassroom;
    ourClassroom = currNode;
  }

  printf("\nHere is the list:\n");
  printf("%-15s %-15s\n", "NAME", "MAJOR");
  printf("--------------- ---------------\n");

  currNode = ourClassroom;
  while(currNode != NULL) {
    printStudent(currNode->data);
    currNode = currNode->next;
  }
  freeList(ourClassroom);
}


// Allocates memory for a new student and initializes it with the given data
void createStudent(char *name, char *major, StudentType **student) {
  *student = (StudentType *) malloc(sizeof(StudentType));
  if (student == NULL) { 
    printf("Memory allocation error\n"); 
    exit(0); 
  }
  strcpy((*student)->name,  name);
  strcpy((*student)->major, major);
}


// Allocates memory for a new list Node
void createNode(NodeType **node, StudentType *data) {
  *node = (NodeType *) malloc(sizeof(NodeType));
  if (node == NULL) { 
    printf("Memory allocation error\n"); 
    exit(0); 
  }
  (*node)->data = data;
  (*node)->next = NULL;
}


// Prints a single student's information
void printStudent(StudentType *sPtr) {
  printf("%-15s %-15s\n", sPtr->name, sPtr->major);
}

// Free all items in a Singly-Linked List 
void freeList(NodeType *aNode) {
  NodeType *nextItem;
  
  while(aNode != NULL) {
    nextItem = aNode->next;
    free(aNode->data);
    free(aNode);
    aNode = nextItem;
  }
}