If you cannot write a binary search routine from scratch, how can you be expected to solve much bigger problems?
void
dumbsort(int *p, int n)
{
for (int tmp, i = 1; i < n; i++) {
if (p[i] < p[i-1]) tmp = p[i], p[i] = p[i-1], p[i-1] = tmp, i = 0;
}
}
void
isort(int *a, size_t n)
{
for (size_t i = 1; i < n; i++) {
for (size_t j = i; j > 0; j--) {
if (a[j-1] <= a[j]) break;
int tmp = a[j];
a[j] = a[j-1];
a[j-1] = tmp;
}
}
}
It took me about five minutes to write that, and it worked the first time I tested it. But that's in part because I find sort routines fascinating and I've been studying them, and programming in C, for almost 30 years. Even if it took you an hour or four hours and required a lot of debugging, you still might be a decent programmer. Especially for jobs where things are less well defined and you have to do a lot of debugging anyway!
(By contrast, I've actually spent most of the last hour trying to write a properly working quicksort, the variant that finishes up with a single call to insertion sort, using both notes and a compiler. Of course it produces correct results because of the final insertion sort but it's not as efficient as it should be and I can't figure out why. Apparently I can't brain today... good thing I'm not in a job interview!)