AtCoder Regular Contest 209 (Div. 1)
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Problem Statement
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Find the number, modulo $998244353$, of strings $S$ of length $N$ consisting of A, B, C such that the following value equals $K$:
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- The maximum length of a (not necessarily contiguous) subsequence of
$S$that does not containABCas a (not necessarily contiguous) subsequence
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You are given $T$ test cases. Solve each of them.
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Constraints
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$1 \le T \le 2 \times 10^5$$1 \le N \le 10^6$$\max(0,N-100) \le K \le N$
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Input
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The input is given from Standard Input in the following format:
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T
\mathrm{case}_1
\mathrm{case}_2
\vdots
\mathrm{case}_T
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Each case is given in the following format:
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N\ K
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Output
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Output $T$ lines. The $i$-th line $(1 \le i \le T)$ should contain the answer to the $i$-th test case.
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样例
Input #1
4
4 3
8 6
123 100
123456 123400
Output #1
9
462
741573397
255048895
For the first test case, for example, `ACBC` satisfies the condition. `ACBC` itself contains `ABC` as a subsequence, and `ACC` does not contain `ABC` as a subsequence, so the maximum length of a subsequence that does not contain `ABC` as a subsequence is $3$. Other examples that satisfy the condition include `AABC` and `ABCA`.
题目信息
题面与样例版权归 AtCoder 及出题人所有;中文翻译由 AI 生成(CI 管线),如有出入请以原文为准。