AtCoder Grand Contest 036
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Problem Statement
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We have a sequence of $N$ integers: $x=(x_0,x_1,\cdots,x_{N-1})$. Initially, $x_i=0$ for each $i$ ($0 \leq i \leq N-1$).
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Snuke will perform the following operation exactly $M$ times:
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- Choose two distinct indices
$i, j$($0 \leq i,j \leq N-1,\ i \neq j$). Then, replace$x_i$with$x_i+2$and$x_j$with$x_j+1$.
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Find the number of different sequences that can result after $M$ operations. Since it can be enormous, compute the count modulo $998244353$.
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Constraints
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$2 \leq N \leq 10^6$$1 \leq M \leq 5 \times 10^5$- All values in input are integers.
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Input
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Input is given from Standard Input in the following format:
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N M
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Output
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Print the number of different sequences that can result after $M$ operations, modulo $998244353$.
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样例
Input #1
2 2
Output #1
3
After two operations, there are three possible outcomes:
- $x=(2,4)$
- $x=(3,3)$
- $x=(4,2)$
For example, $x=(3,3)$ can result after the following sequence of operations:
- First, choose $i=0,j=1$, changing $x$ from $(0,0)$ to $(2,1)$.
- Second, choose $i=1,j=0$, changing $x$ from $(2,1)$ to $(3,3)$.
Input #2
3 2
Output #2
19
Input #3
10 10
Output #3
211428932
Input #4
100000 50000
Output #4
3463133
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。