New Year's Puzzle

题意翻译

给你一个 $2\times n$ 的长方形，里面有 $m$ 的格子被挡住了。 现在有 $T$ 组询问，对于每组询问回答如下问题： - 可不可以**只用** $1\times 2$ 和 $2\times 1$ 的小长方形盖住原来 $2\times n$ 的长方形**没被挡住**的部分。可以输出 `Yes` 否则，输出 `No`。

题目描述

Every year Santa Claus gives gifts to all children. However, each country has its own traditions, and this process takes place in different ways. For example, in Berland you need to solve the New Year's puzzle. Polycarp got the following problem: given a grid strip of size $ 2 \times n $ , some cells of it are blocked. You need to check if it is possible to tile all free cells using the $ 2 \times 1 $ and $ 1 \times 2 $ tiles (dominoes). For example, if $ n = 5 $ and the strip looks like this (black cells are blocked): Then it can be tiled, for example, using two vertical and two horizontal tiles, as in the picture below (different tiles are marked by different colors). And if $ n = 3 $ and the strip looks like this: It is impossible to tile free cells. Polycarp easily solved this task and received his New Year's gift. Can you solve it?

输入输出格式

输入格式

The first line contains an integer $ t $ ( $ 1 \leq t \leq 10^4 $ ) — the number of test cases. Then $ t $ test cases follow. Each test case is preceded by an empty line. The first line of each test case contains two integers $ n $ and $ m $ ( $ 1 \le n \le 10^9 $ , $ 1 \le m \le 2 \cdot 10^5 $ ) — the length of the strip and the number of blocked cells on it. Each of the next $ m $ lines contains two integers $ r_i, c_i $ ( $ 1 \le r_i \le 2, 1 \le c_i \le n $ ) — numbers of rows and columns of blocked cells. It is guaranteed that all blocked cells are different, i.e. $ (r_i, c_i) \ne (r_j, c_j), i \ne j $ . It is guaranteed that the sum of $ m $ over all test cases does not exceed $ 2 \cdot 10^5 $ .

输出格式

For each test case, print on a separate line: - "YES", if it is possible to tile all unblocked squares with the $ 2 \times 1 $ and $ 1 \times 2 $ tiles; - "NO" otherwise. You can output "YES" and "NO" in any case (for example, the strings yEs, yes, Yes and YES will be recognized as positive).

输入输出样例

输入样例 #1

3

5 2
2 2
1 4

3 2
2 1
2 3

6 4
2 1
2 3
2 4
2 6

输出样例 #1

YES
NO
NO

说明

The first two test cases are explained in the statement. In the third test case the strip looks like this:  It is easy to check that the unblocked squares on it can not be tiled.