Codeforces Round 884 (Div. 1 + Div. 2)
E
Great Grids
Codeforces
2400
原题
← DF1 →
翻译中…

An $n \times m$ grid of characters is called great if it satisfies these three conditions:

翻译中…
  • Each character is either 'A', 'B', or 'C'.
  • Every $2 \times 2$ contiguous subgrid contains all three different letters.
  • Any two cells that share a common edge contain different letters.
翻译中…

Let $(x,y)$ denote the cell in the $x$-th row from the top and $y$-th column from the left.

翻译中…

You want to construct a great grid that satisfies $k$ constraints. Each constraint consists of two cells, $(x_{i,1},y_{i,1})$ and $(x_{i,2},y_{i,2})$, that share exactly one corner. You want your great grid to have the same letter in cells $(x_{i,1},y_{i,1})$ and $(x_{i,2},y_{i,2})$.

翻译中…

Determine whether there exists a great grid satisfying all the constraints.

翻译中…

Input

翻译中…

Each test contains multiple test cases. The first line contains the number of test cases $t$ ($1 \le t \le 10^3$). The description of the test cases follows.

翻译中…

The first line of each test case contains three integers, $n$, $m$, and $k$ ($2 \le n,m \le 2 \cdot 10^3$, $1 \le k \le 4 \cdot 10^3$).

翻译中…

Each of the next $k$ lines contains four integers, $x_{i,1}$, $y_{i,1}$, $x_{i,2}$, and $y_{i,2}$ ($1 \le x_{i,1} \lt x_{i,2} \le n$, $1 \le y_{i,1},y_{i,2} \le m$). It is guaranteed that either $(x_{i,2},y_{i,2}) = (x_{i,1}+1,y_{i,1}+1)$ or $(x_{i,2},y_{i,2}) = (x_{i,1}+1,y_{i,1}-1)$.

翻译中…

The pairs of cells are pairwise distinct, i.e. for all $1 \le i \lt j \le k$, it is not true that $x_{i,1} = x_{j,1}$, $y_{i,1} = y_{j,1}$, $x_{i,2} = x_{j,2}$, and $y_{i,2} = y_{j,2}$.

翻译中…

It is guaranteed that the sum of $n$ over all test cases does not exceed $2 \cdot 10^3$.

翻译中…

It is guaranteed that the sum of $m$ over all test cases does not exceed $2 \cdot 10^3$.

翻译中…

It is guaranteed that the sum of $k$ over all test cases does not exceed $4 \cdot 10^3$.

翻译中…

Output

翻译中…

For each test case, output "YES" if a great grid satisfying all the constraints exists and "NO" otherwise.

翻译中…

You can output the answer in any case (upper or lower). For example, the strings "yEs", "yes", "Yes", and "YES" will be recognized as positive responses.

翻译中…

Note

翻译中…

In the first test case, the following great grid satisfies all the constraints:

翻译中…
B A B C
C B C A
A C A B
翻译中…

In the second test case, the two constraints imply that cells $(1,1)$ and $(2,2)$ have the same letter and cells $(1,2)$ and $(2,1)$ have the same letter, which makes it impossible for the only $2 \times 2$ subgrid to contain all three different letters.

翻译中…

样例

Input #1
4
3 4 4
1 1 2 2
2 1 3 2
1 4 2 3
2 3 3 2
2 7 2
1 1 2 2
1 2 2 1
8 5 4
1 2 2 1
1 5 2 4
7 1 8 2
7 4 8 5
8 5 4
1 2 2 1
1 5 2 4
7 1 8 2
7 5 8 4
Output #1
YES
NO
YES
NO
InputCopy OutputCopy
题目信息
题号
1844E
时间限制
1 s
内存限制
256 MB
标签
2-SAT
构造
DFS 及类似
并查集
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。