Question

I have tried (sizeof(array)/sizeof(array[0])). Didn’t work.
I wrote a simple function:

int length(int array[]){
    int i=0;
    while(array[i]) i++;
    return i;
}

Worked one minute, didn’t work the next.

Someone please help! I’m using Xcode as an IDE

Answer 1

The length of an array is not part of the array in C, so when passing an array as a parameter to a function you should pass its length as a parameter too. Here’s an example:

#define ARRLEN(a) (sizeof(a)/sizeof (a)[0]) /* a must be an array, not a pointer */

void printarray(int* a, int alen)
{
    int i;
    for (i = 0; i < alen; i++)
        printf("%d\n", a[i]);
}

main()
{
    int a[] = { 3, 4, 5 };
    printarray(a, ARRLEN(a));
    return 0;
}

However, if your array is defined in such a way as to always end with a sentinel that isn’t normal data, then you can traverse the elements until you encounter the sentinel. e.g.,

void printstrings(char** a)
{
    int i;
    for (i = 0; a[i]; i++)
        printf("%s\n", a[i]);
}

main()
{
    char* a[] = { "This", "should", "work.", NULL };
    printstrings(a);
    return 0;
}