C - Displaying the parts in ascending order by part number - c

Question

I'm new here, so I have no idea if I posted this correctly. I did everything that the instructor told us to do for this program, but this last one has me stumped because we never talked about sorting in class. It says, "Modify the print() function so that it displays the parts sorted in ascending order by part number." I tried looking through the book and on the internet, but I just caused myself to become even more confused. Can anyone help me? Here's my code:
#include <stdio.h>
#include <string.h>
#include <ctype.h>
#define NAME_LEN 25
#define MAX_PARTS 100
struct part {
int number;
char name[NAME_LEN + 1];
int on_hand;
float price;
};
int find_part(int number, const struct part inv[], int np);
void insert(struct part inv[], int *np);
void search(const struct part inv[], int np);
void update(struct part inv[], int np);
void print(const struct part inv[], int np);
int read_line(char [], int);
/**************************************************************
* main: Prompts the user to enter an operation code, *
* then calls a function to perform the requested *
* action. Repeats until the user enters the *
* command 'q'. Prints an error message if the user *
* enters an illegal code. *
**************************************************************/
int main(void)
{
char code;
struct part inventory[MAX_PARTS];
int num_parts = 0;
for (;;)
{
printf("Enter operation code: ");
scanf(" %c", &code);
while (getchar() != '\n') /* skips to end of line */
{
;
}
switch (code)
{
case 'i':
insert(inventory, &num_parts);
break;
case 's':
search(inventory, num_parts);
break;
case 'u':
update(inventory, num_parts);
break;
case 'p':
print(inventory, num_parts);
break;
case 'q':
return 0;
default:
printf("Illegal code\n");
break;
}
printf("\n");
}
}
/************************************************************
* find_part: Looks up a part number in the inv array. *
* Returns the array index if the part number *
* is found; otherwise, returns -1. *
************************************************************/
int find_part(int number, const struct part inv[], int np)
{
int i;
for (i = 0; i < np; i++)
{
if (inv[i].number == number)
{
return i;
}
}
return -1;
}
/****************************************************************
* insert: Prompts the user for information about a new *
* part and then inserts the part into the inv *
* array. Prints an error message and returns *
* prematurely if the part already exists or the *
* array is full. *
****************************************************************/
void insert(struct part inv[], int *np)
{
int part_number;
if (*np == MAX_PARTS)
{
printf("Database is full; can't add more parts.\n");
return;
}
printf("Enter part number: ");
scanf("%d", &part_number);
if (find_part(part_number, inv, *np) >= 0)
{
printf("Part already exists.\n");
return;
}
inv[*np].number = part_number;
printf("Enter part name: ");
read_line(inv[*np].name, NAME_LEN);
printf("Enter quantity on hand: ");
scanf("%d", &inv[*np].on_hand);
printf("Enter the price of the item: ");
scanf("%f", &inv[*np].price);
(*np)++;
}
/************************************************************
* search: Prompts the user to enter a part number, then *
* looks up the part in the inv array. If the *
* part exists, prints the name and quantity on *
* hand; if not, prints an error message. *
************************************************************/
void search(const struct part inv[], int np)
{
int i, number;
printf("Enter part number: ");
scanf("%d", &number);
i = find_part(number, inv, np);
if (i >= 0)
{
printf("Part name: %s\n", inv[i].name);
printf("Quantity on hand: %d\n", inv[i].on_hand);
printf("Item Price: %.2f\n", inv[i].price);
}
else
{
printf("Part not found.\n");
}
}
/*************************************************************
* update: Prompts the user to enter a part number. *
* Prints an error message if the part can't be *
* found in the inv array; otherwise, prompts the *
* user to enter change in quantity on hand and *
* updates the array. *
*************************************************************/
void update(struct part inv[], int np)
{
int i, number, change, userChoice, changePartNum;
float changePrice;
char *changeName[] = {""};
printf("Enter part number: ");
scanf("%d", &number);
i = find_part(number, inv, np);
if (i >= 0)
{
printf("Enter your selection to edit this particular part:\n"
"\t\t Type 1 to change the Part Number\n"
"\t\t Type 2 to change the Part Name\n"
"\t\t Type 3 to change the Price\n"
"\t\t Type 4 to change the Quantity on Hand\n"
"\t\t Type 5 to exit without making changes\n\n"
"\t\t Enter your choice here: ");
scanf("%d", &userChoice);
switch ( userChoice )
{
//printf("Would you like to change the Part Number? \nType 1 for yes or 2 for no.");
//scanf("%d", &userChoice);
case 1:
printf("Enter new part number: ");
scanf("%d", &changePartNum);
inv[i].number = changePartNum;
printf("Change part num: %d\n", changePartNum);
printf("inv[i].number: %d\n", inv[i].number);
break;
//printf("Would you like to change the Part Name? \nType 1 for yes or 2 for no.");
//scanf("%d", &userChoice);
case 2:
printf("Enter new name of part: ");
scanf("%s", changeName);
printf("Change part name: %s\n", changeName);
//strcpy (*changeName, inv[i].name[NAME_LEN + 1]);
//printf("&inv[i].name[NAME_LEN + 1]: %d\n", &inv[i].name[NAME_LEN + 1]);
break;
//printf("Would you like to change the price? \nType 1 for yes or 2 for no.");
//scanf("%d", &userChoice);
case 3:
printf("Enter change in item price: ");
scanf("%f", &changePrice);
inv[i].price = changePrice;
break;
//printf("Would you like to change the quantity on hand? \nType 1 for yes or 2 for no.");
//scanf("%d", &userChoice);
case 4:
printf("Enter change in quantity on hand: ");
scanf("%d", &change);
inv[i].on_hand = change;
break;
case 5:
printf("Exiting the editor.");
break;
default:
printf("Your choice is not on the list.");
break;
}
}
else
{
printf("Part not found.\n");
}
}
/************************************************************
* print: Prints a listing of all parts in the inv array, *
* showing the part number, part name, and *
* quantity on hand. Parts are printed in the *
* order in which they were entered into the *
* array. * *
************************************************************/
void print(const struct part inv[], int np)
{
int i;
printf("Part Number Part Name "
"Quantity on Hand "
" Price\n");
for (i = 0; i < np; i++)
{
printf("%7d\t\t %-5s%31d\t%.2f\n", inv[i].number,
inv[i].name, inv[i].on_hand, inv[i].price);
}
}
/*************************************************************
* read_line: Skips leading white-space characters, then *
* reads the remainder of the input line and *
* stores it in str. Truncates the line if its *
* length exceeds n. Returns the number of *
* characters stored. *
*************************************************************/
int read_line(char str[], int n)
{
int ch = 0;
int i = 0;
while (isspace (ch = getchar()))
{
;
}
while (ch != '\n' && ch != EOF)
{
if (i < n)
{
str[i++] = ch;
}
ch = getchar();
}
str[i] = '\0';
return i;
}

Answer 1

If your professor allows you to use a function from the standard libary, check out C library function to do sort, which provides an answer that shows you how to use qsort(). If you're on linux, you can also get documentation on the function (and other standard library functions) by doing man qsort. If you're not on linux, check out any of the various online man pages.
If not, your professor probably expects you to do your own research. Generally the bubble sort algorithm is taught to beginners because of its simplicity. rosettacode provides pseudo-code on what a bubble sort should look like:
repeat
hasChanged := false
decrement itemCount
repeat with index from 1 to itemCount
if (item at index) > (item at (index + 1))
swap (item at index) with (item at (index + 1))
hasChanged := true
until hasChanged = false
Note that in your print function, you already have all you need, the array and its length. You demonstrated this by looping through it and printing out all the member variables. Now you just need to write the algorithm for the sort. One thing you need for the algorithm is the comparator function. You stated that you need to sort by part number. That means your comparator function will probably look like this:
int compare(struct part a, struct part b)
{
return (a.number < b.number);
}
For qsort():
qsort(inv, np, sizeof(part), compare);
In your sorting algorithm (that you should write yourself):
if (item.number at index) > (item.number at (index + 1))