65. Valid Number

Given a string input_str, determine if it represents a valid number according to the following rules: 1) An integer number may have an optional + or - sign, followed by one or more digits, and may be followed by an optional exponent. 2) A decimal number may have an optional + or - sign, followed by one of: a) digits followed by a dot, b) digits followed by a dot and more digits, c) a dot followed by digits. Both integer and decimal numbers may be followed by an optional exponent. An exponent is e or E followed by an integer number (with optional sign). Return True if input_str is a valid number, otherwise return False.