Arrays and initializing more than one counter

Question

#include <stdio.h>
int main() {
    int niz[100], i, j, k, l;
    j = 0; // k=l=0;
    printf("Unesite niz (-1 for end)");
    do {
        scanf("%d", &niz[i]);
        if (niz[i] % 5 == 0)
            j++;
        // if(niz[i]%7==0) k++;
        // if(niz[i]%11==0) l++;
    } while (niz[i] != -1);
    printf("Broj djeljivih sa 5 je:%d", j);
    // printf("Broj djeljivih sa 7 je:%d",k);
    // printf("Broj djeljivih sa 11 je:%d",l);
    return (0);
}

What's problem with this code, it works fine with comments but when I uncheck comments it gives me a crash. The problem I have is to solve how much numbers are possible to divide by 5,7 and 11.

What happens if you initialize `i`? This sort of weird, unreliable behavior is pretty common with uninitialized variables when they're central, and I don't know where your `scanf()` is writing. — John C, Aug 02 '14 at 19:05
To debug issues like these, look at tools like valgrind, which analyzes possible memory corruptions — tehwallz, Aug 02 '14 at 19:20
Please indent your code so its more readable. Additionally, we will have an easier time understanding it if the comments and variable names are in english. — hugomg, Aug 02 '14 at 19:21

score 1 · Accepted Answer · answered Aug 02 '14 at 19:12

Garbage value @ variable i. So you are trying to reach unindexed part of the array.

Initialize i = 0;
Make sure your loops ends before it again reaches end the array.

do { // Whatever you want to do } while(niz[i]!=-1 && i<100);// Add 1 more condition for i less than 100

score 0 · Answer 2 · answered Aug 03 '14 at 05:29

Since all the variables i, j, k,l are automatic(storage class) integers, by default such variables will have indeterminate (an unspecified value or a trap representation ) value. There fore you need to initialise the variable explicitly.

Moreover, In the code, you are not incrementing the value of "i", then what is the point of using the array. All the input numbers will be stored at niz[i](where "i" may or not be a valid index), thus every new input will overwrite the previous one.

I found the following link to be very useful with respect to your problem.

http://stackoverflow.com/questions/6212921/is-un-initialized-integer-always-default-to-0-in-c

Arrays and initializing more than one counter

2 Answers2