A classical transposition cipher that is, the charcaters in the plaintext are
arranged in a certain order,(here arranged in a zig zag pattern)
and the cipher text is produced by popping all the elements in
the adjacency list row-wise.
The number of rows is to be chosen by the user (generally 3/4/5)

1. user is asked to select either of the two choices (Encryption or Decryption)

2. based on the choice,redirects the user to that particular choice

3. If a plaintext is being encrypted then the user is asked to
   enter the plaintext which is to be encrypted, the encrypted
   text is then displayed on the terminal

4.If a ciphertext is being decrypted then the user is asked to
  enter the ciphertext to be decrypted, the palintext is
  displayed on the terminal

5. The user has to enter the key,remeber the same key value is

   used for both decryption and encryption as in the case of a
   classical cipher.