How to "mark" or "keep" elements of an array?

[stable delta]

The task is to take array size (n) and array elements from stdin. Then check if the element is divisible by its last digit and then output only those elements. I can't use an extra array for this.

#include <stdio.h>
#include <stdlib.h>
#define MAX 100

int main()
{
    int n;
    int a[MAX];
    printf("Enter array length:\n");
    scanf("%d", &n);
    if(n <= 0 || n > MAX)
    {
        printf("Err");
        exit(EXIT_FAILURE);
    }
    for(int i = 0; i < n; i++)
    {
        scanf(" %d", &a[i]);
        int last_digit = a[i] % 10;
        if(a[i] % last_digit == 0)
        {
            printf("%d ", a[i]);
        }
    }
    printf("\n");

    exit(EXIT_SUCCESS);
}

So I'm stuck at the point where I somehow need to mark positions of these digits and keep them or alternatively remove those that don't fit the criteria. Also, there are negative numbers in the array.

[honest carbon]

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[coral sedge]

You don't have to check right when you input the elements.

[stable delta]

Example:
Input: n = 9
a: 173 -25 23 7 17 25 34 61 -4612

Output: -25 7 25 61 -4612

[stable delta]

I don't think I understand. Are you referring to " %d"?

[coral sedge]

No, I mean that you just finish inputting the array, then iterate over it and check each element to output.

[stable delta]

oh you mean I should just do a printf(a[i]) inside of the if statement?

[coral sedge]

No.

First of all, keep only the code that inputs each element in your current for loop.

[stable delta]

ye lol just a printf would do the trick

[ebon musk]

well you need atoi (convert int since everything stdin has everything as bytes) it, save last char of every digit atoi it as well, check remainder and print an output if divisible

[stable delta]

but im not using getchar() and working with characters, only working with digits here

[ebon musk]

I guess that works than

[ebon musk]

if you always expect digits your method works I guess

[stable delta]

Okay I found a way

how to mark the array elements

not just for this task but for any essentially

int func(int array[], int arrayLen)
{
    int i, j, num;
    j = 0;

    for(i = 0; i < n; i++)
    {
        num = abs(array[i]) % 10;

        if(num == 0 || array[i] % num == 0)
        {
            array[j] = array[i];
            j++
        }
    }
    return j;
}

so the new array length will be j

[compact osprey]

abs(x) is useless when doing modular arithmetic

[compact osprey]

the size wouldnt change though

[lethal fjord]

I think that wouldn't be an issue for the task

[compact osprey]

it isnt an issue but as i said the size of the original array wouldnt alter

[lethal fjord]

I like the solution, looks nice 😄
But there is a semicolon missing xD

And... i think i will repeat this again and again, the usage of scanf in the main is currently unsafe xD

[lethal fjord]

i mean, you could do the array dynamically and just realloc it after the for in the function, no?

[compact osprey]

but the array is in the stack

[compact osprey]

look at the second line in main

[lethal fjord]

You can change that from the start?^^

[lethal fjord]

That is what i mean, make that malloc aswell#

[compact osprey]

ah well thats another code then xD

but imo, just printf is enough no need to overwrite the original array

[stable delta]

Yes that's true but it won't matter for this problem. I'm not building a complex program where it would matter but rather solving smaller problems.

[stable delta]

That's correct, just printf would pass the tests but when they open to examine the code they'll probably take away some points on that.

[stable delta]

!solved