Question

This is what I made:

#include <stdio.h>
#include <stdlib.h>

int betweenArray(int a, int b){
    int *arr,i,range;
    range = b - a + 1;
    arr = (int *)malloc(range*sizeof(int));
    for(i=0;i<range;i++){
        arr[i] = a++;
    }
return * arr;

int main (int argc, const char * argv[]) {
    int a,b,i;
    int range;

    printf("Give numbers: ");
    scanf("%d %d",&a,&b);
    range = b - a + 1;


    for(i=0;i<range;i++)
        printf("%d\n",betweenArray(a,b)); 
    return 0;
}

So when I run this and give for example 2 and 5 as arguments I get as a result: 2 2 2 2 instead of 2 3 4 5. I can’t find where I made my mistake.

Answer 1

The problem is that you’re calculating the sequence, but you only return the first number of it.

The return value of betweenArray is int instead of int * and you do return * arr; instead of return arr;. After fixing that, in main, you would need to do:

int *sequence = betweenArray(a,b);
for (i=0;i<range;i++)
    printf("%d", sequence[i];

But it would be better if the function would return the array and the number of elements in it, for example like that:

int *betweenArray(int a, int b, int *numElements){
    int *arr,i,range;
    range = b - a + 1;
    arr = (int *)malloc(range*sizeof(int));
    for(i=0;i<range;i++){
        arr[i] = a++;
    }
    if (numElements) {
        *numElements = range;
    }
    return arr;
}

int main (int argc, const char * argv[]) {
    int a,b,i;
    int *sequence;
    int range;

    printf("Give numbers: ");
    scanf("%d %d",&a,&b);

    sequence = betweenArray(a,b,&range);

    for(i=0;i<range;i++)
        printf("%d\n",sequence[i]);

    free(sequence); // Be nice, clean up.
    return 0;
}