CF2000B Seating in a Bus

In Berland, a bus consists of a row of $ n $ seats numbered from $ 1 $ to $ n $ . Passengers are advised to always board the bus following these rules: - If there are no occupied seats in the bus, a passenger can sit in any free seat; - Otherwise, a passenger should sit in any free seat that has at least one occupied neighboring seat. In other words, a passenger can sit in a seat with index $ i $ ( $ 1 \le i \le n $ ) only if at least one of the seats with indices $ i-1 $ or $ i+1 $ is occupied. Today, $ n $ passengers boarded the bus. The array $ a $ chronologically records the seat numbers they occupied. That is, $ a_1 $ contains the seat number where the first passenger sat, $ a_2 $ — the seat number where the second passenger sat, and so on. You know the contents of the array $ a $ . Determine whether all passengers followed the recommendations. For example, if $ n = 5 $ , and $ a $ = \[ $ 5, 4, 2, 1, 3 $ \], then the recommendations were not followed, as the $ 3 $ -rd passenger sat in seat number $ 2 $ , while the neighboring seats with numbers $ 1 $ and $ 3 $ were free.

The first line of input contains a single integer $ t $ ( $ 1 \le t \le 10^4 $ ) — the number of test cases. The following describes the input test cases. The first line of each test case contains exactly one integer $ n $ ( $ 1 \le n \le 2 \cdot 10^5 $ ) — the number of seats in the bus and the number of passengers who boarded the bus. The second line of each test case contains $ n $ distinct integers $ a_i $ ( $ 1 \le a_i \le n $ ) — the seats that the passengers occupied in chronological order. It is guaranteed that the sum of $ n $ values across all test cases does not exceed $ 2 \cdot 10^5 $ , and that no passenger sits in an already occupied seat.

For each test case, output on a separate line: - "YES", if all passengers followed the recommendations; - "NO" otherwise. You may output the answer in any case (for example, the strings "yEs", "yes", "Yes", and "YES" will be recognized as a positive answer).

The first test case is explained in the problem statement.