Thread: Split positive and negative numbers from one array into two arrays

Hi,

I've been toiling over this problem for about two weeks, and I'll be the first to admit I have no idea what I'm doing. I'm in a beginner C programming class that I only needed to take for graduating, so I'm not a programmer and I don't want to be one.

That said, I don't mind the challenge, it's just that this is getting frustrating.

So the problem is this:

Define an array w/ 20 integer values, fill array with numbers (input or hard-coded)
Write function called split() to read array and put all + #s in "positive" array and - #s into "negative" array
Call a function to display values in both positive & negative arrays
Extend program to sort positive & negative arrays in ascending order before they are displayed

I created the major array with 20 values and put the numbers in there. I kind of wrote the split() function except I probably did everything wrong. What I did was piece together different parts from the section on Arrays in my textbook as far as I understood them, and it's not working right.

Here's my code:

Code:

#include <stdio.h>
#define MAXELS 20

int split(int [], int, int); 

int main()
{
	int vals[MAXELS] = {12, 34, -43, 4, -34, 0, 11, 23, 46, 33, -67, 90, 100, 13, -16, 29, 17, 18, 19, 20} ;
	int value;
	
	value = split(vals, MAXELS, 0); 
	
	return 0; 
}

int split(int num[], int pos, int neg)
{
	int x, y; 
	
		
	for (x = 0; x < MAXELS; x++) 
		if (num[x] >= 0)
			num[x] = num[pos];
	for (y = 0; y < MAXELS; y++) 
		if (num[y] <= 0)
			num[y] = num[neg];
			
	printf("Positive numbers: \n", x); 
	printf("Negative numbers: ", y); 
	
	return (x, y);
}

It compiles but the Positive Numbers: and Negative Numbers: print out nothing.

I most likely am missing a concept (or several) here, but I have my textbook open to the Arrays chapter and I'm willing to learn if anyone is kind enough to help me out. I'm kind of embarrassed to throw my code out there because it probably makes NO sense! Thanks in advance though!

Hi Dino, thanks for your reply.

I kind of understood what you meant about overlaying the array, but not entirely, sorry about that... can you give me an example of what you mean?

I modified my code a little, hopefully not for the worse.

Code:

int split(int []); 

int main()
{
	int vals[MAXELS] = {12, 34, -43, 4, -34, 0, 11, 23, 46, 33, -67, 90, 100, 13, -16, 29, 17, 18, 19, 20} ;
	int value;
	
	value = split(vals); 
	
	return 0; 
}

int split(int num[])
{
	int i;  
	int pos;
	int neg; 
		
	for (i = 0; i < MAXELS; i++) 
		if (num[i] >= 0)
			pos = num[i];
		else
			neg = num[i];
			
	printf("Positive numbers: \n", pos); 
	printf("Negative numbers: ", neg); 
	
	return (pos, neg);
}

Thanks for clarifying, NeonBlack. I understand what you mean about using pointers. But is there a way to do it without pointers?

I'm just asking because the section in my textbook does not use pointers in its functions in the example problems.

Oh geez I feel stupid

Gotta put %d in the printf statements. That'll do something more than what it does now at least...

So, I got it to do what I want, kind of.

It displays which numbers are positive in my vals array, and which ones are negative.

Code:

#include <stdio.h>
#define MAXELS 20

int split(int []); 

int main()
{
	int vals[MAXELS] = {12, 34, -43, 4, -34, 0, 11, 23, 46, 33, -67, 90, 100, 13, -16, 29, 17, 18, 19, 20} ;
	int value;
	
	value = split(vals); 
	
	return 0; 
}

int split(int num[])
{
	int x, y;  
	int pos; 
	int neg; 

	for (x = 0; x < MAXELS; x++)
		
		if (num[x] >= 0)
			printf("%d\n", pos = num[x]); 
			
	for (y = 0; y < MAXELS; y++)
		if (num[y] < 0)
			printf("%d\n ", neg = num[y]);
			
	
}

Output:
12
34
4
0
11
23
46
33
90
100
13
29
17
18
19
20
-43
-34
-67
-16


It kind of does what the problem asks ( probably not all the way, but at least SOMETHING happens), and I don't even want to try putting these numbers in ascending order. My brain is hurting enough! But if you want to give me more information feel free to do so, every bit helps.

Originally Posted by grumpy

Instead of printing out the value, incorporate some logic to copy the value into the appopriate (positive or negative) array.

Personally, if the original order of values in the input array doesn't matter, my first step would be to sort the whole array before picking values to put into different arrays. The negative and positive values would then be easy to find .....

Actually if he sorted it in ascending order, all he needs to do is find the first positive value and set a pointer to it... now he effectively has two arrays split by the pointer.

Originally Posted by CommonTater

Actually if he sorted it in ascending order, all he needs to do is find the first positive value and set a pointer to it... now he effectively has two arrays split by the pointer.

Tater, you always favor the positive numbers -- it ain't fair!!