Codeforces Round 706 (Div. 1)
C
Garden of the Sun
Codeforces
2300
原题
← BD →
翻译中…

There are many sunflowers in the Garden of the Sun.

翻译中…

Garden of the Sun is a rectangular table with $n$ rows and $m$ columns, where the cells of the table are farmlands. All of the cells grow a sunflower on it. Unfortunately, one night, the lightning stroke some (possibly zero) cells, and sunflowers on those cells were burned into ashes. In other words, those cells struck by the lightning became empty. Magically, any two empty cells have no common points (neither edges nor corners).

翻译中…

Now the owner wants to remove some (possibly zero) sunflowers to reach the following two goals:

翻译中…
  • When you are on an empty cell, you can walk to any other empty cell. In other words, those empty cells are connected.
  • There is exactly one simple path between any two empty cells. In other words, there is no cycle among the empty cells.
翻译中…

You can walk from an empty cell to another if they share a common edge.

翻译中…

Could you please give the owner a solution that meets all her requirements?

翻译中…

Note that you are not allowed to plant sunflowers. You don't need to minimize the number of sunflowers you remove. It can be shown that the answer always exists.

翻译中…

Input

翻译中…

The input consists of multiple test cases. The first line contains a single integer $t$ ($1\le t\le 10^4$) — the number of test cases. The description of the test cases follows.

翻译中…

The first line contains two integers $n$, $m$ ($1 \le n,m \le 500$) — the number of rows and columns.

翻译中…

Each of the next $n$ lines contains $m$ characters. Each character is either 'X' or '.', representing an empty cell and a cell that grows a sunflower, respectively.

翻译中…

It is guaranteed that the sum of $n \cdot m$ for all test cases does not exceed $250\,000$.

翻译中…

Output

翻译中…

For each test case, print $n$ lines. Each should contain $m$ characters, representing one row of the table. Each character should be either 'X' or '.', representing an empty cell and a cell with a sunflower, respectively.

翻译中…

If there are multiple answers, you can print any. It can be shown that the answer always exists.

翻译中…

Note

翻译中…

Let's use $(x,y)$ to describe the cell on $x$-th row and $y$-th column.

翻译中…

In the following pictures white, yellow, and blue cells stand for the cells that grow a sunflower, the cells lightning stroke, and the cells sunflower on which are removed, respectively.

翻译中…

image

翻译中…

In the first test case, one possible solution is to remove sunflowers on $(1,2)$, $(2,3)$ and $(3 ,2)$.

翻译中…

image

翻译中…

Another acceptable solution is to remove sunflowers on $(1,2)$, $(2,2)$ and $(3,2)$.

翻译中…

image

翻译中…

This output is considered wrong because there are 2 simple paths between any pair of cells (there is a cycle). For example, there are 2 simple paths between $(1,1)$ and $(3,3)$.

翻译中…
  1. $(1,1)\to (1,2)\to (1,3)\to (2,3)\to (3,3)$
  2. $(1,1)\to (2,1)\to (3,1)\to (3,2)\to (3,3)$
翻译中…

image

翻译中…

This output is considered wrong because you can't walk from $(1,1)$ to $(3,3)$.

翻译中…

样例

Input #1
5
3 3
X.X
...
X.X
4 4
....
.X.X
....
.X.X
5 5
.X...
....X
.X...
.....
X.X.X
1 10
....X.X.X.
2 2
..
..
Output #1
XXX
..X
XXX
XXXX
.X.X
.X..
.XXX
.X...
.XXXX
.X...
.X...
XXXXX
XXXXXXXXXX
..
..
InputCopy OutputCopy
题目信息
题号
1495C
时间限制
1 s
内存限制
256 MB
标签
构造
图论

题面与样例版权归 Codeforces 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。