C - Alphabetically sorting arrays error - c

Question

I'm working on a phone book assignment for my CECS class and I ran into a problem with alphabetically sorting the contacts. The program will allow me to sort up to 3 contacts, however when I try to sort more than 3, the program starts spitting out garbage variables and possibly crashing.
void Sort(phone *phonebook, int *num_entries)
{
int tracker = *num_entries;
if (tracker >= 0)
{
phone *temp = (phone*) calloc(tracker, sizeof(phone));
if (temp== NULL)
printf("\n\nOut of memory\n\n");
else
{
int i, j;
for (i = 0; i < tracker; i++)
{
for (j = i+1; j < tracker; j++)
{
//Combines first and last names into 1 name for easy comparison
strcpy(phonebook[i].totalname, phonebook[i].fName);
strcpy(phonebook[j].totalname, phonebook[j].fName);
strcat(phonebook[i].totalname, phonebook[i].lName);
strcat(phonebook[j].totalname, phonebook[j].lName);
printf("\nTotal name = %s\nTotal name = %s", phonebook[i].totalname, phonebook[j].totalname); //Done so I can verify it worked correctly
if (strcmp(phonebook[i].totalname, phonebook[j].totalname) > 0)
{
strcpy(temp[i].fName, phonebook[i].fName);
strcpy(temp[i].lName, phonebook[i].lName);
temp[i].number = phonebook[i].number;
temp[i].area = phonebook[i].area;
strcpy(phonebook[i].fName, phonebook[j].fName);
strcpy(phonebook[i].lName, phonebook[j].lName);
phonebook[i].number = phonebook[j].number;
phonebook[i].area = phonebook[j].area;
strcpy(phonebook[j].fName, temp[i].fName);
strcpy(phonebook[j].lName, temp[i].lName);
phonebook[j].number = temp[i].number;
phonebook[j].area = temp[i].area;
}
}
}
printf("\n\nSuccessfully sorted!\n\n");
}
}
else
printf("\n\nYou need people in the phone book before you can sort it.\n\n");
}
-------------------------
typedef struct PhoneBook
{
char fName[20];
char lName[20];
char totalname[40];
float number;
int area;
} phone;
Edited to add the structure. And I don't use qsort because we haven't learned about it in class and the TA's are rather strict about not using stuff we haven't learned.
void Add(phone *phonebook, int *num_entries)
{
int tracker = *num_entries;
if (tracker == 0)
{
printf("\n\nSomething's wrong here\n\n");
}
else
{
const int newSize = tracker + 1;
phone *temp = (phone*) realloc(phonebook, (newSize * sizeof(phone)));
if (temp!=NULL)
{
phonebook = temp;
}
else
phonebook = NULL;
}
if (phonebook == NULL)
printf("\n\nOut of memory, can't add more to your phonebook\n\n");
else
{
printf("\n\nEnter the first name: ");
scanf("%s", phonebook[tracker].fName);
printf("\nPlease enter the last name: ");
scanf("%s", phonebook[tracker].lName);
printf("\nPlease enter the area code: ");
scanf("%d", &phonebook[tracker].area);
printf("\nPlease enter the phone number (no dashes allowed): ");
scanf("%f", &phonebook[tracker].number);
*num_entries += 1;
printf("\nContact Added.\n\n");
}
}
Edited again to show the code to add people to the phone book (also broken). After 3-4 entries, it starts placing garbage values for entries.
int main()
{
int userInput = 8; //means exit
int num_entries = 1;
phone *phonebook = (phone*) calloc(1 , sizeof(phone));
if (phonebook == NULL)
printf("\n\nOut of memory\n\n");
else
{
do
{
system("cls");
printf("Menu: \n");
printf("1) Add a Contact\n");
printf("2) Delete a Contact\n");
printf("3) Display Phone Book\n");
printf("4) Alphabetically Sort\n");
printf("5) Find a Contact\n");
printf("6) Random Contact\n");
printf("7) Delete All\n");
printf("8) Exit\n\n");
scanf(" %d", &userInput);
switch (userInput)
{
case 1: //Add a Friend
Add(phonebook, &num_entries);
break;
case 2: //Delete a Friend
Delete(phonebook, &num_entries);
break;
case 3: //List all contacts
Display(phonebook, &num_entries);
break;
case 4:
Sort(phonebook, &num_entries);
break;
case 5:
Find(phonebook, &num_entries);
break;
case 6:
Random(phonebook, &num_entries);
break;
case 7:
DeleteAll(phonebook, &num_entries);
break;
case 8:
free(phonebook);
break;
}
system("PAUSE");
}while(userInput != 8);
}
return 0;
}
Edited to show the calls for each function
Well I can't post photos without more reputation so here's the links:
Photo 1 - Adding 3 contacts works fine: http://s980.photobucket.com/user/valondon/media/C%20Realloc%20Errors/Erroronerealloc_zpsc8228131.png.html?sort=3&o=0
Photo 2 - The phone book after the fourth contact was added: http://s980.photobucket.com/user/valondon/media/C%20Realloc%20Errors/Errorthreerealloc_zps246b76e3.png.html?sort=3&o=2

Answer 1

Problem is with the outer loop.
If you have say 'n' entries in the array to sort, then you have to compare the first entry of the array with remaining 'n-1' entries. After first entry is compared with all 'n-1' entries that means first entry is properly located at its location in sorted array. Now you have left with 'n-1' entries to sort. Now if you want to compare 2nd entry of the array then you have to compare that 2nd entry with remaining 'n-1-1' (only 'n-1' entries left to sort and you have taken 2nd entry to compare with rest of the entries). this goes on till the end.
In your code you can change the code like below (the loop part):
Note: I have created a temp variable of temp of structure phone.
phone temp;
for (i = 0; i < tracker - 1; i++)
{
for (j = i+1; j <= tracker - 1; j++)
{
//Combines first and last names into 1 name for easy comparison
strcpy(phonebook[i].totalname, phonebook[i].fName);
strcpy(phonebook[j].totalname, phonebook[j].fName);
strcat(phonebook[i].totalname, phonebook[i].lName);
strcat(phonebook[j].totalname, phonebook[j].lName);
printf("\nTotal name = %s\nTotal name = %s", phonebook[i].totalname, phonebook[j].totalname); //Done so I can verify it worked correctly
if (strcmp(phonebook[i].totalname, phonebook[j].totalname) > 0)
{
strcpy(temp.fName, phonebook[i].fName);
strcpy(temp.lName, phonebook[i].lName);
temp.number = phonebook[i].number;
temp.area = phonebook[i].area;
strcpy(phonebook[i].fName, phonebook[j].fName);
strcpy(phonebook[i].lName, phonebook[j].lName);
phonebook[i].number = phonebook[j].number;
phonebook[i].area = phonebook[j].area;
strcpy(phonebook[j].fName, temp.fName);
strcpy(phonebook[j].lName, temp.lName);
phonebook[j].number = temp.number;
phonebook[j].area = temp.area;
}
}
}
printf("\n\nSuccessfully sorted!\n\n");
}

Answer 2

The problem is with your for loops.
In your example, j is equal to i+1 in the second loop. i has a maximum value of tracker - 1, so j can be equal to tracker. This will cause you to overshoot the array, which can trash memory.
Try changing them to:
for (i = 0; i < tracker - 1; i++)
{
for (j = 0; j < tracker - i - 1; j++)
The other issue is that in your inner loop, you are using [i] and [j] to index your swaps. If you change every [i] in that loop to [j+1], you'll have a working bubble sort.
Your inner loop ends up as:
phone temp; /* I created a stack variable called temp - saves the need for allocation */
for (i = 0; i < tracker - 1; i++)
{
for (j = 0; j < tracker - i - 1; j++)
{
//Combines first and last names into 1 name for easy comparison
strcpy(phonebook[j+1].totalname, phonebook[j+1].fName);
strcpy(phonebook[j].totalname, phonebook[j].fName);
strcat(phonebook[j+1].totalname, phonebook[j+1].lName);
strcat(phonebook[j].totalname, phonebook[j].lName);
printf("\nTotal name = %s\nTotal name = %s", phonebook[j+1].totalname, phonebook[j].totalname); //Done so I can verify it worked correctly
if (strcmp(phonebook[j+1].totalname, phonebook[j].totalname) > 0)
{
strcpy(temp.fName, phonebook[j+1].fName);
strcpy(temp.lName, phonebook[j+1].lName);
temp.number = phonebook[j+1].number;
temp.area = phonebook[j+1].area;
strcpy(phonebook[j+1].fName, phonebook[j].fName);
strcpy(phonebook[j+1].lName, phonebook[j].lName);
phonebook[j+1].number = phonebook[j].number;
phonebook[j+1].area = phonebook[j].area;
strcpy(phonebook[j].fName, temp.fName);
strcpy(phonebook[j].lName, temp.lName);
phonebook[j].number = temp.number;
phonebook[j].area = temp.area;
}
}
}