Numbers From Strangers

Implement validated numeric parsing: ``c /* parse a decimal int in [min,max]; 0 ok, -1 on: NULL/empty, any non-digit character (leading '-' allowed iff it yields a value >= min), or value outside [min,max]. No leading whitespace, no '+', no trailing junk. */ int parse_range(const char *s, long min, long max, long *out); ``

Difficulty: intermediate