Perform lexical operations that are usually best implemented with a Finite Automata (or Finite State Machine). Make sure to start by writing out the grammar for each problem.

Write a program in C++ to convert a character representation of a non-negative number to an integer value without using the string-to-integer conversions available in some languages (you must do a character-by-character conversion). Use a separate method to do the actual conversion. A possible method signature is:

int convert(String s);

Note the ASCII characters for 0 through 9 are in order, so in C/C++, Java, or C#, you can convert a digit to its numeric value by subtracting 0 (and subtracting ?0 in Ruby). E.g., if the digit is in character c, the expression c - '0' will give the numeric value of that digit. In C++/C, you can use isdigit(c) to detect a digit. It is in in C++ ( in C). In Java, there is a similar method in the Character class.

Do not use hardcoded numbers for ASCII values of digits or any other characters.