Typical Interview Problem (Codeforces 1796A)
Tags: Implement, strings

The FB-string is formed as follows. Initially, it is empty. We go through all positive integers, starting from $$$1$$$, in ascending order, and do the following for each integer:  if the current integer is divisible by $$$3$$$, append F to the end of the FB-string;  if the current integer is divisible by $$$5$$$, append B to the end of the FB-string. Note that if an integer is divisible by both $$$3$$$ and $$$5$$$, we append F, and then B, not in the opposite order.The first $$$10$$$ characters of the FB-string are FBFFBFFBFB: the first F comes from the integer $$$3$$$, the next character (B) comes from $$$5$$$, the next F comes from the integer $$$6$$$, and so on. It's easy to see that this string is infinitely long. Let $$$f_i$$$ be the $$$i$$$-th character of FB-string; so, $$$f_1$$$ is F, $$$f_2$$$ is B, $$$f_3$$$ is F, $$$f_4$$$ is F, and so on.You are given a string $$$s$$$, consisting of characters F and/or B. You have to determine whether it is a substring (contiguous subsequence) of the FB-string. In other words, determine if it is possible to choose two integers $$$l$$$ and $$$r$$$ ($$$1 \le l \le r$$$) so that the string $$$f_l f_{l+1} f_{l+2} \dots f_r$$$ is exactly $$$s$$$.For example:  FFB is a substring of the FB-string: if we pick $$$l = 3$$$ and $$$r = 5$$$, the string $$$f_3 f_4 f_5$$$ is exactly FFB;  BFFBFFBF is a substring of the FB-string: if we pick $$$l = 2$$$ and $$$r = 9$$$, the string $$$f_2 f_3 f_4 \dots f_9$$$ is exactly BFFBFFBF;  BBB is not a substring of the FB-string. 

Input: The first line contains one integer $$$t$$$ ($$$1 \le t \le 2046$$$) — the number of test cases.Each test case consists of two lines. The first line contains one integer $$$k$$$ ($$$1 \le k \le 10$$$) — the number of characters in $$$s$$$. The second line contains $$$s$$$, which is a string of exactly $$$k$$$ characters. Each character of $$$s$$$ is either F or B.

Output: For each test case, print YES if $$$s$$$ is a substring of the FB-string, or NO otherwise.You may print each letter in any case (YES, yes, Yes will all be recognized as positive answer, NO, no and nO will all be recognized as negative answer).


Sample Inputs:
3
3
FFB
8
BFFBFFBF
3
BBB

Sample Outputs:
YES
YES
NO

Solution (Python):
""""""
tp = 'FBFFBFFBFBFFBFFBFB'

def i():
    n = int(input())
    s = input()
    if s in tp:
        return 'YES\n'
    return 'NO\n'
t = int(input())
a = []
for _ in range(t):
    a.append(i())
print(''.join(a), end='')

Solution (Python):
for s in [*open(0)][2::2]:
    print('NYOE S'[s[:-1] in 'FBFFBFFB' * 3::2])

Solution (Python):
for s in [*open(0)][2::2]:
    print('NYOE S'[s[:-1] in 'FBFFBFFB' * 3::2])