Given a string of text that contains lowercase letters, encode it as follows: (I will be using abcdef)

  • First, encode the alphabet cipher, but this time, 0-indexed. 000102030405
  • Reverse it. 504030201000
  • Loop through the string.
    • If the next two digits together are 25 or smaller, encode those two numbers. 5 04 03 02 01 00 0
    • Otherwise, encode one number. f e d c b a a
  • Join. fedcbaa

Test cases

abcdef                          fedcbaa
abcdefghijklmnopqrstuvwxyz      fyxwvucjsrqponmlktihgfedcbaa
helloworld                      dbromylloha
ppcg                            gcfpb
codegolf                        fboqedema
programmingpuzzlesandcodegolf   fboqedemddkiobpzuzqdscmkhqerpb

Encoder (not golfed)

Remember, this is , so the code with the fewest bytes wins.

  • 1
    \$\begingroup\$ I get different answers for some of the test cases. For example, codegolf becomes 0214030406141105, reversing to 5011416040304120, split as 5,01,14,16,04,03,04,12,0 turning into fboqedema instead of fbobgedema as you have. \$\endgroup\$ – Gabriel Benamy Nov 6 '16 at 23:50
  • \$\begingroup\$ @GabrielBenamy Fixed. Thank you for telling me. \$\endgroup\$ – Oliver Ni Nov 7 '16 at 1:39

Perl, 73 + 2 = 75 bytes

Run with the -lp flag


JavaScript, 126 125 bytes


Try it online!


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