Cockroach Salad

Cockroach Salad is a card game designed by Jacques Zeimet in 2007. The rules are as follows:

• When you play a card, if there is no restriction, you must say the name of the vegetable printed on your card.
• However, you can not say the same name twice in a row. If you can not say the correct vegetable, you must say say an arbitrary different vegetable.
• One vegetable name is banned and you can not say it. If you would need to say it, say an arbitrary different vegetable.

In this challenge, we’ll have 4 vegetables: a (lettuce), b (tomato), c (cucumber), and d (grape). Given the order you draw cards from the deck, output what vegetables you would say out out. If there are capital letters A, B, C, D in the input, those mean that vegetable is now banned. Do not include these in the output. One vegetable is banned at a time, a new banned vegetable replaces the last one.

Worked Out Example

Lets take the input: aabAaacd

• First, we see an a. This is valid so we output a.
• Then we get an a again. We can not say a twice in a row, so we output b. We could have also outputted c or d and it would also be valid.
• Next, we see b. However, we can’t output b twice in a row so we output d. We could have also outputted a or c.
• Now we see an A. This is a capital so it means a is now banned. We output nothing.
• Then we get an a, but a is banned. d was last outputted so we can’t print that either. So we output c.
• Then another a. We output d, since a is banned.
• Next, c. c is valid so we must output c.
• Next, d, which is also valid.

So the final output could be abadcdcd, but there are other valid options.

Each line in the input will be one string.