solve in C++

18. Developing secret codes has interested people for centuries. A simple coding scheme can be developed by replacing each character in a text file by another character that is a fixed number of positions away in the collating sequence. For example, if each character is replaced by the character that is two characters to its right in the alpha- bet, then the letter a is replaced by the letter c, the letter b is replaced by the letter d and so on. Write a program that reads the text in a file file that contains the coded text using this scheme. Change only the alphanumeric characters. and then generates a new