Problem 1: Encryption and decryption

Given an integer N, we want to write a program to encrypt and to decrypt N.

The encryption rules are:

1) Determine A, the number of digits of N

Example : N = 6789, then A=4

2) Determine reversedN which is formed by the digits of the number N read from right to left

Example N = 1234, then reversedN=4321

3) Calculate the integer N2 which is defined as :

N2 = 10^A-1reversedN

Example : N = 1234, reversedN=4321, N2 = 10000 1 4321 = 5678

4) Calculate N_enc (the encrypted number) the number obtained by concatenating A and N2

Example : N = 1234, N2 = 5678, then N_enc = 45678, the number 4 in bold fonts is the value of

A

Examples :

N = 100654321, N_enc = 9876543998

N = 100873109, N_enc = 9098621998

In the two previous examples, the number 9 in bold fonts is the value of A.

Q1) Write the pseudo-code to decrypt N_enc

Q2) Write the C++ code to encryp and to decrypt (have two cpp files, one for each operation). For the

encryption step, the user will provide an integer N >0 and which may have up to 12 digits (ie. A <= 12).

In C++, you must use the type : long instead of int, in order to manipulate numbers of 12 digits or

more.

Your code must not use arrays