Codeforces Round 785 (Div. 2) |
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Finished |
Let's call a string $$$s$$$ perfectly balanced if for all possible triplets $$$(t,u,v)$$$ such that $$$t$$$ is a non-empty substring of $$$s$$$ and $$$u$$$ and $$$v$$$ are characters present in $$$s$$$, the difference between the frequencies of $$$u$$$ and $$$v$$$ in $$$t$$$ is not more than $$$1$$$.
For example, the strings "aba" and "abc" are perfectly balanced but "abb" is not because for the triplet ("bb",'a','b'), the condition is not satisfied.
You are given a string $$$s$$$ consisting of lowercase English letters only. Your task is to determine whether $$$s$$$ is perfectly balanced or not.
A string $$$b$$$ is called a substring of another string $$$a$$$ if $$$b$$$ can be obtained by deleting some characters (possibly $$$0$$$) from the start and some characters (possibly $$$0$$$) from the end of $$$a$$$.
The first line of input contains a single integer $$$t$$$ ($$$1\leq t\leq 2\cdot 10^4$$$) denoting the number of testcases.
Each of the next $$$t$$$ lines contain a single string $$$s$$$ ($$$1\leq |s|\leq 2\cdot 10^5$$$), consisting of lowercase English letters.
It is guaranteed that the sum of $$$|s|$$$ over all testcases does not exceed $$$2\cdot 10^5$$$.
For each test case, print "YES" if $$$s$$$ is a perfectly balanced string, and "NO" otherwise.
You may print each letter in any case (for example, "YES", "Yes", "yes", "yEs" will all be recognized as positive answer).
5 aba abb abc aaaaa abcba
YES NO YES YES NO
Let $$$f_t(c)$$$ represent the frequency of character $$$c$$$ in string $$$t$$$.
For the first testcase we have
$$$t$$$ | $$$f_t(a)$$$ | $$$f_t(b)$$$ |
$$$a$$$ | $$$1$$$ | $$$0$$$ |
$$$ab$$$ | $$$1$$$ | $$$1$$$ |
$$$aba$$$ | $$$2$$$ | $$$1$$$ |
$$$b$$$ | $$$0$$$ | $$$1$$$ |
$$$ba$$$ | $$$1$$$ | $$$1$$$ |
For the second testcase we have
$$$t$$$ | $$$f_t(a)$$$ | $$$f_t(b)$$$ |
$$$a$$$ | $$$1$$$ | $$$0$$$ |
$$$ab$$$ | $$$1$$$ | $$$1$$$ |
$$$abb$$$ | $$$1$$$ | $$$2$$$ |
$$$b$$$ | $$$0$$$ | $$$1$$$ |
$$$bb$$$ | $$$0$$$ | $$$2$$$ |
For the third testcase we have
$$$t$$$ | $$$f_t(a)$$$ | $$$f_t(b)$$$ | $$$f_t(c)$$$ |
$$$a$$$ | $$$1$$$ | $$$0$$$ | $$$0$$$ |
$$$ab$$$ | $$$1$$$ | $$$1$$$ | $$$0$$$ |
$$$abc$$$ | $$$1$$$ | $$$1$$$ | $$$1$$$ |
$$$b$$$ | $$$0$$$ | $$$1$$$ | $$$0$$$ |
$$$bc$$$ | $$$0$$$ | $$$1$$$ | $$$1$$$ |
$$$c$$$ | $$$0$$$ | $$$0$$$ | $$$1$$$ |
It can be seen that for any substring $$$t$$$ of $$$s$$$ and any two characters $$$u,v\in\{a,b,c\}$$$, the difference between $$$f_t(u)$$$ and $$$f_t(v)$$$ is not more than $$$1$$$. Hence the string $$$s$$$ is perfectly balanced.
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