You are given an $$$n \times n$$$ grid where each cell has a label of $$$0$$$ or $$$1$$$. You are given $$$q$$$ operations, each specifying a cell whose label is flipped (from $$$0$$$ to $$$1$$$, or from $$$1$$$ to $$$0$$$). After each operation, determine whether it is possible to travel from cell $$$(1, 1)$$$ to cell $$$(n, n)$$$ by only traversing cells labeled $$$1$$$, moving between adjacent cells.
This problem must be solved online. Each query is given as a cell $$$(x, y)$$$, but the true cell is determined using the previous $$$\mathrm{num}$$$ answers. Specifically, you are given $$$\mathrm{num}$$$ pairs $$$(u_i, v_i)$$$ for $$$i = 0, 1, \ldots, 2^{\mathrm{num}} - 1$$$. Let $$$\mathrm{val}$$$ be the integer formed by writing the previous $$$\mathrm{num}$$$ answers in order from oldest to most recent as a binary string, where $$$\text{YES} = 1$$$ and $$$\text{NO} = 0$$$, and interpreting it as a binary number with the oldest answer as the most significant bit and the most recent answer as the least significant bit. Any answer that does not yet exist is treated as $$$\text{NO}$$$. Then the true cell is: $$$$$$x' = \begin{cases} x + u_{\mathrm{val}} - n & \text{if } x + u_{\mathrm{val}} \gt n \\ x + u_{\mathrm{val}} & \text{otherwise} \end{cases}$$$$$$ $$$$$$y' = \begin{cases} y + v_{\mathrm{val}} - n & \text{if } y + v_{\mathrm{val}} \gt n \\ y + v_{\mathrm{val}} & \text{otherwise} \end{cases}$$$$$$
The first line contains a single integer $$$n$$$ ($$$1 \le n \le 2000$$$).
The next $$$n$$$ lines each consist of a length $$$n$$$ binary string, representing the initial state of the $$$n \times n$$$ grid.
The next line contains two integers $$$q$$$ and $$$\mathrm{num}$$$ ($$$1 \le q \le 2000$$$, $$$1 \le \mathrm{num} \le 15$$$).
The next $$$2^{\mathrm{num}}$$$ lines each contain two integers $$$u_i$$$ and $$$v_i$$$ ($$$0 \le u_i, v_i \lt n$$$).
The next $$$q$$$ lines each contain two integers $$$x$$$ and $$$y$$$ ($$$1 \le x, y \le n$$$), denoting the cell to flip.
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Tests are numbered from $$$1-20$$$ and each test is worth $$$5$$$ points.
Tests $$$1-2$$$ satisfy $$$n, q \le 500$$$.
Tests $$$3-8$$$ satisfy $$$\mathrm{num} = 1$$$ and $$$u_0, u_1, v_0, v_1 = 0$$$. That is, you can solve the problem offline.
Tests $$$9-20$$$ satisfy no additional constraints.
Output $$$q$$$ lines, where the $$$i$$$-th line contains "YES" or "NO" indicating whether cell $$$(1,1)$$$ can reach cell $$$(n,n)$$$ after the $$$i$$$-th operation.
3 101 010 111 3 1 0 2 1 1 3 2 1 3 2 2
NO YES NO
5 01010 11111 11011 10100 11011 5 1 0 0 0 0 1 1 5 3 5 4 4 5 2 2
NO YES NO YES NO
For the first sample, the points that are actually operated after the online constraint are $$$(3,1), (1,2), (3,3)$$$
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Problem Idea: willy108
Problem Preparation: gg_gong
Occurrences: Advanced K