codeforces#P2003A. Turtle and Good Strings
Turtle and Good Strings
Description
Turtle thinks a string $s$ is a good string if there exists a sequence of strings $t_1, t_2, \ldots, t_k$ ($k$ is an arbitrary integer) such that:
- $k \ge 2$.
- $s = t_1 + t_2 + \ldots + t_k$, where $+$ represents the concatenation operation. For example, $\texttt{abc} = \texttt{a} + \texttt{bc}$.
- For all $1 \le i < j \le k$, the first character of $t_i$ isn't equal to the last character of $t_j$.
Turtle is given a string $s$ consisting of lowercase Latin letters. Please tell him whether the string $s$ is a good string!
Each test contains multiple test cases. The first line contains the number of test cases $t$ ($1 \le t \le 500$). The description of the test cases follows.
The first line of each test case contains a single integer $n$ ($2 \le n \le 100$) — the length of the string.
The second line of each test case contains a string $s$ of length $n$, consisting of lowercase Latin letters.
For each test case, output "YES" if the string $s$ is a good string, and "NO" otherwise.
You can output the answer in any case (upper or lower). For example, the strings "yEs", "yes", "Yes", and "YES" will be recognized as positive responses.
Input
Each test contains multiple test cases. The first line contains the number of test cases $t$ ($1 \le t \le 500$). The description of the test cases follows.
The first line of each test case contains a single integer $n$ ($2 \le n \le 100$) — the length of the string.
The second line of each test case contains a string $s$ of length $n$, consisting of lowercase Latin letters.
Output
For each test case, output "YES" if the string $s$ is a good string, and "NO" otherwise.
You can output the answer in any case (upper or lower). For example, the strings "yEs", "yes", "Yes", and "YES" will be recognized as positive responses.
4
2
aa
3
aba
4
abcb
12
abcabcabcabc
No
nO
Yes
YES
Note
In the first test case, the sequence of strings $\texttt{a}, \texttt{a}$ satisfies the condition $s = t_1 + t_2 + \ldots + t_k$, but the first character of $t_1$ is equal to the last character of $t_2$. It can be seen that there doesn't exist any sequence of strings which satisfies all of the conditions, so the answer is "NO".
In the third test case, the sequence of strings $\texttt{ab}, \texttt{cb}$ satisfies all of the conditions.
In the fourth test case, the sequence of strings $\texttt{abca}, \texttt{bcab}, \texttt{cabc}$ satisfies all of the conditions.