Codeforces Round 800 (Div. 2) |
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Finished |
Let's call a binary string $$$T$$$ of length $$$m$$$ indexed from $$$1$$$ to $$$m$$$ paranoid if we can obtain a string of length $$$1$$$ by performing the following two kinds of operations $$$m-1$$$ times in any order :
For example, if $$$T = $$$ 001, we can select the substring $$$[T_2T_3]$$$ and perform the first operation. So we obtain $$$T = $$$ 01.
You are given a binary string $$$S$$$ of length $$$n$$$ indexed from $$$1$$$ to $$$n$$$. Find the number of pairs of integers $$$(l, r)$$$ $$$1 \le l \le r \le n$$$ such that $$$S[l \ldots r]$$$ (the substring of $$$S$$$ from $$$l$$$ to $$$r$$$) is a paranoid string.
The first line contains an integer $$$t$$$ ($$$1 \le t \le 1000$$$) — the number of test cases. The description of test cases follows.
The first line of each test case contains a single integer $$$n$$$ ($$$1 \le n \le 2 \cdot 10^5$$$) — the size of $$$S$$$.
The second line of each test case contains a binary string $$$S$$$ of $$$n$$$ characters $$$S_1S_2 \ldots S_n$$$. ($$$S_i = $$$ 0 or $$$S_i = $$$ 1 for each $$$1 \le i \le n$$$)
It is guaranteed that the sum of $$$n$$$ over all test cases doesn't exceed $$$2 \cdot 10^5$$$.
For each test case, output the number of pairs of integers $$$(l, r)$$$ $$$1 \le l \le r \le n$$$ such that $$$S[l \ldots r]$$$ (the substring of $$$S$$$ from $$$l$$$ to $$$r$$$) is a paranoid string.
511201310041001511111
1 3 4 8 5
In the first sample, $$$S$$$ already has length $$$1$$$ and doesn't need any operations.
In the second sample, all substrings of $$$S$$$ are paranoid. For the entire string, it's enough to perform the first operation.
In the third sample, all substrings of $$$S$$$ are paranoid except $$$[S_2S_3]$$$, because we can't perform any operations on it, and $$$[S_1S_2S_3]$$$ (the entire string).
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