Given a string s representing a number, determine if it is a valid number. A valid number can be split into the following components (in order): 1. A decimal number or an integer. 2. (Optional) An 'e' or 'E', followed by an integer. A decimal number can be split into the following components (in order): 1. (Optional) A sign character (either '+' or '-'). The following formats are allowed: * One or more digits, followed by a dot '.'. * One or more digits, followed by a dot '.', followed by one or more digits. * A dot '.', followed by one or more digits. An integer can be split into the following components (in order): * (Optional) A sign character (either '+' or '-'). * One or more digits. For example, the following are valid numbers: ["2", "0089", "-0.1", "+3.14", "4.", "-.9", "2e10", "-90E3", "3e+7", "+6e-1", "53.5e93", "-123.456e789"], while the following are not valid numbers: ["abc", "1a", "1e", "e3", "99e2.5", "--6", "-+3", "95a54e53"]. Given a string s, return "YES" if s is a valid number.