Codeforces Round 676 (Div. 2)
B
Putting Bricks in the Wall
Codeforces
1100
原题
← AC →
翻译中…

Pink Floyd are pulling a prank on Roger Waters. They know he doesn't like walls, he wants to be able to walk freely, so they are blocking him from exiting his room which can be seen as a grid.

翻译中…

Roger Waters has a square grid of size $n\times n$ and he wants to traverse his grid from the upper left ($1,1$) corner to the lower right corner ($n,n$). Waters can move from a square to any other square adjacent by a side, as long as he is still in the grid. Also except for the cells ($1,1$) and ($n,n$) every cell has a value $0$ or $1$ in it.

翻译中…

Before starting his traversal he will pick either a $0$ or a $1$ and will be able to only go to cells values in which are equal to the digit he chose. The starting and finishing cells ($1,1$) and ($n,n$) are exempt from this rule, he may go through them regardless of picked digit. Because of this the cell ($1,1$) takes value the letter 'S' and the cell ($n,n$) takes value the letter 'F'.

翻译中…

For example, in the first example test case, he can go from ($1, 1$) to ($n, n$) by using the zeroes on this path: ($1, 1$), ($2, 1$), ($2, 2$), ($2, 3$), ($3, 3$), ($3, 4$), ($4, 4$)

翻译中…

The rest of the band (Pink Floyd) wants Waters to not be able to do his traversal, so while he is not looking they will invert at most two cells in the grid (from $0$ to $1$ or vice versa). They are afraid they will not be quick enough and asked for your help in choosing the cells. ** Note that you cannot invert cells $(1, 1)$ and $(n, n)$**.

翻译中…

We can show that there always exists a solution for the given constraints.

翻译中…

Also note that Waters will pick his digit of the traversal after the band has changed his grid, so he must not be able to reach ($n,n$) no matter what digit he picks.

翻译中…

Input

翻译中…

Each test contains multiple test cases. The first line contains the number of test cases $t$ ($1 \le t \le 50$). Description of the test cases follows.

翻译中…

The first line of each test case contains one integers $n$ ($3 \le n \le 200$).

翻译中…

The following $n$ lines of each test case contain the binary grid, square ($1, 1$) being colored in 'S' and square ($n, n$) being colored in 'F'.

翻译中…

The sum of values of $n$ doesn't exceed $200$.

翻译中…

Output

翻译中…

For each test case output on the first line an integer $c$ ($0 \le c \le 2$)  — the number of inverted cells.

翻译中…

In $i$-th of the following $c$ lines, print the coordinates of the $i$-th cell you inverted. You may not invert the same cell twice. ** Note that you cannot invert cells $(1, 1)$ and $(n, n)$**.

翻译中…

Note

翻译中…

For the first test case, after inverting the cell, we get the following grid:

翻译中…

S010
0001
1001
111F

翻译中…

样例

Input #1
3
4
S010
0001
1000
111F
3
S10
101
01F
5
S0101
00000
01111
11111
0001F
Output #1
1
3 4
2
1 2
2 1
0
InputCopy OutputCopy
题目信息
题号
1421B
时间限制
1 s
内存限制
256 MB
标签
构造
模拟

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。