I have to break up the following code into the following files: main.c, student.c, students.h, mergesort.c, mergesort.h, aux.c and aux.h. I then have to make a makefile to compile it all.
The program is a mergesort implemented on a linked list. I've separated up the code, but I have no clue as to what to do in terms of headers files and include directives, and even less of a clue as to how to create the makefile. What do I need to include for the headers files, and what do I need to include in the C files? As an example, if mergesort.c is using functions from students.c, would I have to include students.h in mergesort.c? Here's the code for the original program:
#include <stdio.h>
#include <stdlib.h>
#define NAME_LEN 25
struct node {
int number;
char name[NAME_LEN+1];
struct node* next;
};
/* The functions to manage the linked list. The functions prompt the
user and read the standard input if needed. */
struct node* insert (struct node* student_list);
void print_student (struct node* student);
void print_list (struct node* student_list);
void search (struct node* student_list);
struct node* delete (struct node* student_list);
void delete_list (struct node* student_list);
/* Merge sort */
struct node* mergesort(struct node* student_list);
struct node* merge (struct node* list1, struct node *list2);
/* Auxiliary functions */
int read_line(char line[], int len); /* Read at most len characters
from the standard input and
ignore the rest of the line. */
int line_skip(); /* Read the standard input to the end of the line. */
int line_copy(); /* Read the standard input to the end of the line
and copy to the standard output. */
int pause(); /* Ask user to press Enter to continue. */
int main() {
int option;
struct node* student_list = NULL;
for (;;) {
printf("
-- OPTIONS MENU -----------------
");
printf("1: Add a student
");
printf("2: Search for a student by number
");
printf("3: Delete a student by number
");
printf("4: Display all students
");
printf("5: Sort students by number
");
printf("0: Exit
");
printf("
");
printf("Enter an option: ");
if ( scanf("%d", &option) != 1 ) {
if ( feof(stdin) ) break;
printf("Invalid option: "); line_copy(); pause();
continue;
}
/* Read the rest of the line after option number. Usually, it is
just one new-line character */
line_skip();
if (option == 0) break;
switch(option) {
case 1: student_list = insert(student_list); break;
case 2: search(student_list); break;
case 3: student_list = delete(student_list); break;
case 4: print_list(student_list); break;
case 5: student_list = mergesort(student_list); break;
default:
printf("Incorrect option: %d
", option); pause();
}
}
delete_list(student_list); /* Not necessary in this example */
printf("Bye!
");
return 0;
}
struct node* mergesort(struct node* student_list) {
struct node* list1 = student_list;
struct node* list2 = student_list;
if (student_list == NULL || student_list->next == NULL)
return student_list;
while ((list2 = list2->next) != NULL &&
(list2 = list2->next) != NULL)
list1 = list1->next;
list2 = list1->next;
list1->next = NULL ;
list1 = student_list;
list1 = mergesort(list1);
list2 = mergesort(list2);
return merge(list1, list2);
}
struct node* merge(struct node* list1, struct node* list2) {
struct node *list, *prev;
if (list1 == NULL) return list2;
if (list2 == NULL) return list1;
if (list1->number <= list2->number) {
list = list1; list1 = list1->next;
} else {
list = list2; list2 = list2->next;
}
prev = list;
while (list1 != NULL && list2 != NULL) {
if (list1->number <= list2->number) {
prev->next = list1;
list1 = list1->next;
} else {
prev->next = list2;
list2 = list2->next;
}
prev = prev->next ;
}
if (list1 != NULL)
prev->next = list1;
else
prev->next = list2;
return list;
}
struct node* insert(struct node* student_list) {
struct node* student = malloc(sizeof(struct node));
/* Why would it be incorrect to use "struct node student;" ? */
if (student == NULL ) {
printf("Out of memory for a new student!
"); pause();
return student_list;
}
printf("
Adding a new student
");
printf("Enter student's number: ");
if (scanf("%d", &student->number) != 1) {
printf("Incorrect student number: ");
line_copy(); pause();
free(student); /**/
return student_list;
}
line_skip(); /* to skip the newline character */
printf("Enter student's name: ");
read_line(student->name, NAME_LEN);
student->next = student_list;
printf("Student %d added.
", student->number); pause();
return student;
}
void print_student(struct node* student) {
printf("Number:%3d Name: %s
", student->number, student->name);
}
void print_list(struct node* student_list) {
printf("
Student List:
");
while (student_list != NULL) {
print_student(student_list);
student_list = student_list->next;
}
pause();
}
void search(struct node* student_list) {
int number;
printf("Enter student number: ");
if (scanf("%d", &number) != 1) {
printf("Incorrect student number: ");
line_copy(); pause();
return;
}
line_skip();
while (student_list != NULL && number != student_list->number)
student_list = student_list->next;
if (student_list == NULL)
printf("Not found.
");
else
print_student(student_list);
pause();
}
struct node* delete(struct node* student_list) {
int number;
struct node *prev, *cur;
printf("Enter student number: ");
if (scanf("%d", &number) != 1) {
printf("Incorrect student number: "); line_copy(); pause();
return student_list;
}
line_skip();
for (cur = student_list, prev = NULL;
cur != NULL && cur -> number != number;
prev = cur, cur = cur->next)
;
if (cur == NULL) {
printf("Student not found!
"); pause();
return student_list;
}
if (prev == NULL)
student_list = student_list->next;
else
prev->next = cur->next;
free(cur);
return student_list;
}
void delete_list(struct node* student_list) {
struct node* temp;
while (student_list != NULL) {
temp = student_list;
student_list = student_list->next;
free(temp);
}
}
/*Auxiliary Function
int read_line(char line[], int len) {
int ch, i = 0;
while ((ch = getchar()) != '
' && ch != EOF)
if (i < len)
line[i++] = ch;
line[i] = '';
return i;
}
int line_skip() {
int ch;
while ( (ch=getchar()) != '
' && ch != EOF )
;
return ch != EOF;
}
int line_copy() {
int ch;
while ( (ch=getchar()) != '
' && ch != EOF )
putchar(ch);
putchar('
');
return ch != EOF;
}
int pause() {
printf("Press Enter to continue...");
return line_skip();
}
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