AtCoder Regular Contest 142
B
Unbalanced Squares
AtCoder
⌀ 692
原题
← AC →
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Problem Statement

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We have an $N \times N$ grid. Let $(i,j)$ denote the square at the $i$-th row from the top and $j$-th column from the left in this grid. Find one way to write an integer on every square to satisfy the conditions below.

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  • Each integer between $1$ and $N^2$ is written exactly once.
  • For every pair of integers $i,j\, (1 \leq i,j \leq N)$, the square $(i,j)$ satisfies the following.
  • Among the squares horizontally, vertically, or diagonally adjacent to $(i,j)$ (there are at most eight of them), let $a$ and $b$ be the number of squares with integers larger than and smaller than that of $(i,j)$, respectively. Then, $a \neq b$ holds.
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Under the Constraints of this problem, it can be proved that such a way to write integers always exists.

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Constraints

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  • $2 \leq N \leq 500$
  • $N$ is an integer.
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Input

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Input is given from Standard Input in the following format:

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N

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Output

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Print a way to write integers to satisfy the conditions, in the following format:

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x_{1,1} \ldots x_{1,N}
\vdots
x_{N,1} \ldots x_{N,N}

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Here, $x_{i,j}$ is the integer to write on the square $(i,j)$. If multiple solutions exist, any of them will be accepted.

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样例

Input #1
2
Output #1
1 2
3 4
This output contains each integer between $1$ and $N^2\, (=4)$ exactly once, so the first condition is satisfied. Additionally, among the squares horizontally, vertically, or diagonally adjacent to the square $(1,1)$, three squares $(1,2)$, $(2,1)$, and $(2,2)$ have integers larger than that of $(1,1)$, and none has an integer smaller than that. Thus, for $(1,1)$, we have $a=3$ and $b=0$, so $a\neq b$ holds. Similarly, it can be verified that $a\neq b$ also holds for the other squares, so the second condition is satisfied. Therefore, this output is valid.
Input #2
3
Output #2
1 2 3
5 4 6
7 8 9
题目信息
题号
arc142_b
时间限制
2 s
内存限制
1024 MB

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。