ST:Pls help for this programing problem in c++ (standard IO without file read/write),better with some comment about why coding that way,thanks

Problem A: Secret text Time limit:2 sec Problem Description Write a program to translate a secret text. The text is encrypted by the following rules. First if the text is a lowercase letter, we translate it into an uppercase letter, and the first letter 'a' is translate into the last letter "Z', the second letter 'b' is translated into the second to the last letter 'Y", and so on. If the text is an uppercase letter, we translate it into a lowercase letter similarly. If we see a digit, we will translate it into the next digit, and the only exception is "9, which will be translated into "O. On all other cases, the text is not changed. Input File Format The input is lines of text. Output Format The output is the text after translation. Example Sample Input: This is a test line. We have roughly 59 characters in this example. Sample Output: gSRH RH Z GVHG ORMV. dV SZEV ILFTSOB 60 XSZIZXGVIH RM GSRH VCZNKOV