CF1384A Common Prefixes

The length of the longest common prefix of two strings $ s = s_1 s_2 \ldots s_n $ and $ t = t_1 t_2 \ldots t_m $ is defined as the maximum integer $ k $ ( $ 0 \le k \le min(n,m) $ ) such that $ s_1 s_2 \ldots s_k $ equals $ t_1 t_2 \ldots t_k $ . Koa the Koala initially has $ n+1 $ strings $ s_1, s_2, \dots, s_{n+1} $ . For each $ i $ ( $ 1 \le i \le n $ ) she calculated $ a_i $ — the length of the longest common prefix of $ s_i $ and $ s_{i+1} $ . Several days later Koa found these numbers, but she couldn't remember the strings. So Koa would like to find some strings $ s_1, s_2, \dots, s_{n+1} $ which would have generated numbers $ a_1, a_2, \dots, a_n $ . Can you help her? If there are many answers print any. We can show that answer always exists for the given constraints.

Each test contains multiple test cases. The first line contains $ t $ ( $ 1 \le t \le 100 $ ) — the number of test cases. Description of the test cases follows. The first line of each test case contains a single integer $ n $ ( $ 1 \le n \le 100 $ ) — the number of elements in the list $ a $ . The second line of each test case contains $ n $ integers $ a_1, a_2, \ldots, a_n $ ( $ 0 \le a_i \le 50 $ ) — the elements of $ a $ . It is guaranteed that the sum of $ n $ over all test cases does not exceed $ 100 $ .

For each test case: Output $ n+1 $ lines. In the $ i $ -th line print string $ s_i $ ( $ 1 \le |s_i| \le 200 $ ), consisting of lowercase Latin letters. Length of the longest common prefix of strings $ s_i $ and $ s_{i+1} $ has to be equal to $ a_i $ . If there are many answers print any. We can show that answer always exists for the given constraints.

In the $ 1 $ -st test case one of the possible answers is $ s = [aeren, ari, arousal, around, ari] $ . Lengths of longest common prefixes are: - Between $ \color{red}{a}eren $ and $ \color{red}{a}ri $ $ \rightarrow 1 $ - Between $ \color{red}{ar}i $ and $ \color{red}{ar}ousal $ $ \rightarrow 2 $ - Between $ \color{red}{arou}sal $ and $ \color{red}{arou}nd $ $ \rightarrow 4 $ - Between $ \color{red}{ar}ound $ and $ \color{red}{ar}i $ $ \rightarrow 2 $