C solutions initial

[AKJ7]

I just wanted to contribute by providing my C solutions.

[nayuki]

Rejected - see my policy.

[nayuki]

While well-intentioned, your code is incorrect in these places:

• You used a variable with type size_t to hold the answer, and the C standard only mandates that size_t is unsigned and at least 16 bits wide. The answer for Problem 1 is 233168. If size_t is indeed the same as uint16_t (max is 65535), then the answer overflows the variable. You were probably hoping that size_t would be the widest integer type available on the platform (like 64 bits), but this is by no means guaranteed.
• Calling printf() with a size_t value requires the specifier %zu, not %lu as in your code.