If in a certain language, ‘ORANGE’ is coded as ‘QTCPIG’, then ‘YCVGTOGNQP’ is…

In letter-shift (Caesar-style) coding, every letter of the original word is replaced by another letter that lies a fixed number of positions ahead in the English alphabet. Decoding simply reverses this rule: each coded letter is moved back by that same fixed number of positions to recover the original letter.

Comparing ORANGE with its given code QTCPIG letter by letter fixes the exact shift used, which can then be reversed to decode YCVGTOGNQP.

1. O (15th letter) becomes Q (17th letter): a forward shift of 2.

2. R (18th letter) becomes T (20th letter): a forward shift of 2.

3. A (1st letter) becomes C (3rd letter): a forward shift of 2.

4. N (14th letter) becomes P (16th letter): a forward shift of 2.

5. G (7th letter) becomes I (9th letter): a forward shift of 2.

6. E (5th letter) becomes G (7th letter): a forward shift of 2.

Every letter shifts forward by exactly 2 positions, so the coding rule is: replace each letter with the letter 2 places ahead in the alphabet.

1. Y (25th letter) shifted back 2 places gives W (23rd letter).

2. C (3rd letter) shifted back 2 places gives A (1st letter).

3. V (22nd letter) shifted back 2 places gives T (20th letter).

4. G (7th letter) shifted back 2 places gives E (5th letter).

5. T (20th letter) shifted back 2 places gives R (18th letter).

6. O (15th letter) shifted back 2 places gives M (13th letter).

7. G (7th letter) shifted back 2 places gives E (5th letter).

8. N (14th letter) shifted back 2 places gives L (12th letter).

9. Q (17th letter) shifted back 2 places gives O (15th letter).

10. P (16th letter) shifted back 2 places gives N (14th letter).

Reading the recovered letters in order gives W, A, T, E, R, M, E, L, O, N, that is, WATERMELON. As a check, shifting every letter of WATERMELON forward by 2 places reproduces Y, C, V, G, T, O, G, N, Q, P exactly, confirming the decode.