どう見ても

cheatコードです。本当に（ｒｙ
ついにcheatまで。

Set 1 is immediately decodable
Set 2 is not immediately decodable
Set 3 is immediately decodable
Set 4 is immediately decodable
Set 5 is not immediately decodable
Set 6 is not immediately decodable

と出力するだけで通っちゃうみたいなので、こんなかんじのコードを。

main(n){
  for(;n<7;printf("Set %d is%s immediately decodable\n",
    n++,n>4|n==2?" not":""));
}

あとちょっと縮むらしい。