Codeforces Round 614 (Div. 1)
A
NEKO's Maze Game
Codeforces
1400
原题
←B →
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NEKO#ΦωΦ has just got a new maze game on her PC!

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The game's main puzzle is a maze, in the forms of a $2 \times n$ rectangle grid. NEKO's task is to lead a Nekomimi girl from cell $(1, 1)$ to the gate at $(2, n)$ and escape the maze. The girl can only move between cells sharing a common side.

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However, at some moments during the game, some cells may change their state: either from normal ground to lava (which forbids movement into that cell), or vice versa (which makes that cell passable again). Initially all cells are of the ground type.

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After hours of streaming, NEKO finally figured out there are only $q$ such moments: the $i$-th moment toggles the state of cell $(r_i, c_i)$ (either from ground to lava or vice versa).

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Knowing this, NEKO wonders, after each of the $q$ moments, whether it is still possible to move from cell $(1, 1)$ to cell $(2, n)$ without going through any lava cells.

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Although NEKO is a great streamer and gamer, she still can't get through quizzes and problems requiring large amount of Brain Power. Can you help her?

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Input

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The first line contains integers $n$, $q$ ($2 \le n \le 10^5$, $1 \le q \le 10^5$).

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The $i$-th of $q$ following lines contains two integers $r_i$, $c_i$ ($1 \le r_i \le 2$, $1 \le c_i \le n$), denoting the coordinates of the cell to be flipped at the $i$-th moment.

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It is guaranteed that cells $(1, 1)$ and $(2, n)$ never appear in the query list.

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Output

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For each moment, if it is possible to travel from cell $(1, 1)$ to cell $(2, n)$, print "Yes", otherwise print "No". There should be exactly $q$ answers, one after every update.

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You can print the words in any case (either lowercase, uppercase or mixed).

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Note

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We'll crack down the example test here:

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  • After the first query, the girl still able to reach the goal. One of the shortest path ways should be: $(1,1) \to (1,2) \to (1,3) \to (1,4) \to (1,5) \to (2,5)$.
  • After the second query, it's impossible to move to the goal, since the farthest cell she could reach is $(1, 3)$.
  • After the fourth query, the $(2, 3)$ is not blocked, but now all the $4$-th column is blocked, so she still can't reach the goal.
  • After the fifth query, the column barrier has been lifted, thus she can go to the final goal again.
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样例

Input #1
5 5
2 3
1 4
2 4
2 3
1 4
Output #1
Yes
No
No
No
Yes
InputCopy OutputCopy
题目信息
题号
1292A
时间限制
1.5 s
内存限制
256 MB
标签
数据结构
并查集
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。