An Array of Arrays - arrays

Question

I want to store a group of arrays containing 2 numbers in an array. But I only want 2 numbers to be stored when 5 followed by a comma and another number is entered. Essentially, what I want my program to do is read from this array of arrays and perform tasks accordingly. So if the user enters 2, I want to store (2,0) in one space of my array and move on to ask my user for the second number. But if the user types 5,10 I want the program to store (5,10) in that same array. Then my program could filter which array has only one value and which has 2 and do different tasks accordingly. My assignment requires us to not ask 2 numbers for each array which would have made it easier.
This is what I have so far and I know I'm wrong I just don't know where to go from here:
int main(void)
{
int size = 0;
int input;
int factor;
int mdArrays[100][2];
for (size_t i = 0; i < 100; i++)
{
size = i;
scanf("%d,%d", &input, &factor);
if (input != 5 && input != 9)
{
factor = 0;
for (size_t j =0 ; j< 2; j++)
{
mdArrays[i] = input;
mdArrays[j] = factor;
}
}
else if (input == 9)
{
break;
}
else
{
for(int j = 0; j< 2; j++)
{
mdArrays[i] = input;
mdArrays[j] = factor;
}
}
}
for (size_t i =0; i < size; i++)
{
for(size_t j = 0; j < 2; j++)
{
printf("%d,%d", mdArrays[i[j]]);
}
}
}

Answer 1

There were a few issues.
size is one too short (it should be i + 1).
It may be possible to handle 5 vs 5,23 using scanf. But, I prefer to use fgets and strtol and check the delimiter (e.g. whether it's , or not).
The if/else ladder logic can be simplified if we make the first test against input == 9 to stop the loop.
According to your code, you want to force a factor of zero if input != 5. That doesn't make much sense to me, but I've kept that logic [for now].
That may not be what you want/need, but it was my best interpretation of your code. The main purpose is to differentiate how many numbers are on a given line. So, adjust the rest as needed.
I think the way you're storing/displaying the array is incorrect. I believe you want to store input into mdArrays[i][0] and factor into mdArrays[i][1]. Using j makes no sense to me.
As I mentioned [in my top comments], the printf in the final loop is invalid.
Note that the code is cleaner if we don't hardwire the dimensions with a literal 100 in multiple places (e.g. once in the myArrays declaration and again in the outer for loop). Better to use (e.g.) #define MAXCOUNT 100 and replace 100 elsewhere with MAXCOUNT (see below).
I created three versions. One that is annotated with original and fixed code. Another that removes the original code. And, a third that organizes the data using a struct.
Here's the refactored code. I've bracketed your/old code [vs. my/new code] with:
#if 0
// old code
#else
// new code
#endif
I added a debug printf. Anyway, here's the code with some annotations:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int
main(void)
{
int size = 0;
int input;
int factor;
int mdArrays[100][2];
for (size_t i = 0; i < 100; i++) {
#if 0
size = i;
scanf("%d,%d",&input,&factor);
#else
// get line
char buf[100];
char *cp = fgets(buf,sizeof(buf),stdin);
if (cp == NULL)
break;
// strip newline -- only needed for debug print
cp = strchr(buf,'\n');
if (cp != NULL)
*cp = 0;
// decode first number
input = strtol(buf,&cp,10);
// decode second number if it exists -- otherwise, use a sentinel
if (*cp == ',')
factor = strtol(cp + 1,&cp,10);
else
factor = -1;
printf("DEBUG: buf='%s' input=%d factor=%d\n",buf,input,factor);
#endif
// stop input if we see the end marker
if (input == 9)
break;
// remember number of array elements
size = i + 1;
// only use a non-zero factor if input is _not_ 5
if (input != 5) {
factor = 0;
#if 0
for (size_t j = 0; j < 2; j++) {
mdArrays[i] = input;
mdArrays[j] = factor;
}
continue;
#endif
}
#if 0
for (int j = 0; j < 2; j++) {
mdArrays[i] = input;
mdArrays[j] = factor;
}
#else
mdArrays[i][0] = input;
mdArrays[i][1] = factor;
#endif
}
for (size_t i = 0; i < size; i++) {
#if 0
for (size_t j = 0; j < 2; j++) {
printf("%d,%d",mdArrays[i[j]]);
}
#else
printf("%d,%d\n",mdArrays[i][0],mdArrays[i][1]);
#endif
}
return 0;
}
Here's the sample input I used to test:
5,3
7,6
8,9
5,37
5
9,23
Here's the program output:
DEBUG: buf='5,3' input=5 factor=3
DEBUG: buf='7,6' input=7 factor=6
DEBUG: buf='8,9' input=8 factor=9
DEBUG: buf='5,37' input=5 factor=37
DEBUG: buf='5' input=5 factor=-1
DEBUG: buf='9,23' input=9 factor=23
5,3
7,0
8,0
5,37
5,-1
Here's a slightly cleaned up version:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define MAXCOUNT 100
int
main(void)
{
int size = 0;
int input;
int factor;
int mdArrays[MAXCOUNT][2];
for (size_t i = 0; i < MAXCOUNT; i++) {
// get line
char buf[100];
char *cp = fgets(buf,sizeof(buf),stdin);
if (cp == NULL)
break;
// strip newline -- only needed for debug print
#ifdef DEBUG
cp = strchr(buf,'\n');
if (cp != NULL)
*cp = 0;
#endif
// decode first number
input = strtol(buf,&cp,10);
// decode second number if it exists -- otherwise, use a sentinel
if (*cp == ',')
factor = strtol(cp + 1,&cp,10);
else
factor = -1;
#ifdef DEBUG
printf("DEBUG: buf='%s' input=%d factor=%d\n",buf,input,factor);
#endif
// stop input if we see the end marker
if (input == 9)
break;
// remember number of array elements
size = i + 1;
// only use a non-zero factor if input is _not_ 5
if (input != 5)
factor = 0;
mdArrays[i][0] = input;
mdArrays[i][1] = factor;
}
for (size_t i = 0; i < size; i++)
printf("%d,%d\n",mdArrays[i][0],mdArrays[i][1]);
return 0;
}
You might benefit from using a struct [YMMV], so here's a version that keeps things organized that way:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define MAXCOUNT 100
typedef struct {
int input;
int factor;
} data_t;
int
main(void)
{
int size = 0;
data_t mdArrays[MAXCOUNT];
data_t *data;
for (size_t i = 0; i < MAXCOUNT; i++) {
// get line
char buf[100];
char *cp = fgets(buf,sizeof(buf),stdin);
if (cp == NULL)
break;
// strip newline -- only needed for debug print
#ifdef DEBUG
cp = strchr(buf,'\n');
if (cp != NULL)
*cp = 0;
#endif
data = &mdArrays[i];
// decode first number
data->input = strtol(buf,&cp,10);
// decode second number if it exists -- otherwise, use a sentinel
if (*cp == ',')
data->factor = strtol(cp + 1,&cp,10);
else
data->factor = -1;
#ifdef DEBUG
printf("DEBUG: buf='%s' input=%d factor=%d\n",buf,input,factor);
#endif
// stop input if we see the end marker
if (data->input == 9)
break;
// remember number of array elements
size = i + 1;
// only use a non-zero factor if input is _not_ 5
if (data->input != 5)
data->factor = 0;
}
for (size_t i = 0; i < size; i++) {
data = &mdArrays[i];
printf("%d,%d\n",data->input,data->factor);
}
return 0;
}

Answer 2

Read a line of user input with fgets() and then parse it to see if it is one number, two comma separated numbers or something else.
I recommend using `"%n" to detect when and how scanning finished.
int get_numbers(int *input, int *factor) {
char buf[80];
if (fgets(buf, sizeof buf, stdin)) {
int n = 0;
sscanf(buf, "%d %n", input, &n);
if (n > 0 && buf[n] == '\0') return 1;
n = 0;
sscanf(buf, "%d ,%d %n", input, factor, &n);
if (n > 0 && buf[n] == '\0') return 2;
return 0; // Invalid input
}
return EOF; // No input
}
Usage
// scanf("%d,%d", &input, &factor);
switch (get_numbers(&input, &factor)) {
case 2: printf("%d %d\n", input, factor); break;
case 1: printf("%d\n", input); break;
case 0: printf("Invalid input\n"); break;
case EOF: printf("No input\n"); break;
}