No.3100 Parallel Translated
Problem Statement
You are given a convex polygon $P$ with $N$ vertices in $2$-dimensional Euclidean space. The vertices of $P$ are numbered as vertices $1, 2, \cdots, N$. Vertex $i$ $(1\le i \le N)$ is located at coordinates $(X_i, Y_i)$, and the edges of $P$ consist of the $N$ edges connecting vertex $i$ and vertex $i+1$. Here, vertex $N+1$ refers to vertex $1$.
Take $2$ real numbers uniformly at random from the range of at least $0$ and less than $1$, and let them be $p, q$. Find the expected value, $\mathrm{mod} ~ {998244353}$, of the number of lattice points contained in the interior of the polygon
$$Q = \{(x+p, y+q) \mid (x, y) \in P\}$$
obtained by translating every point contained in $P$ by $(p, q)$.
Notes
It can be proved that the expected value to be found is always a rational number. It can also be proved that, under the constraints of this problem, when this value is expressed as an irreducible fraction $\frac{P}{Q}$ with coprime positive integers $P, Q$, we have $Q \not \equiv 0 \pmod{998244353}$. Then, an integer $R$ satisfying $R \times Q \equiv P \pmod{998244353}$ and $0 \le R < 998244353$ is uniquely determined, so report this $R$.
Constraints
- All input values are integers.
- $3 \le N \le 100$
- $P$ is a convex polygon.
- The area of $P$ is positive.
- $-10^6 \le X_i, Y_i \le 10^6$
- $(X_1, Y_1), \cdots, (X_N, Y_N)$ are the vertices of $P$ given in counterclockwise order (with the positive direction of the $x$-axis pointing right and the positive direction of the $y$-axis pointing up).
- $(X_i, Y_i), (X_{i+1}, Y_{i+1}), (X_{i+2}, Y_{i+2})$ do not lie on a single straight line. Here, $(X_{N+1}, Y_{N+1})$ denotes $(X_1, Y_1)$ and $(X_{N+2}, Y_{N+2})$ denotes $(X_2, Y_2)$. $(1 \le i \le N)$
Input
$N$ $X_1$ $Y_1$ $\vdots$ $X_N$ $Y_N$
Output
Output the answer.Sample
Sample 1
Input
3 1 1 0 2 -1 0
Output
499122178
The polygon $P$ is as follows:
The lattice points with a positive probability of being contained in the polygon $Q$ are the following $4$ points.
- $(0,1)$: The necessary and sufficient condition for it to be contained in the interior of $Q$ is $0 \lt a, b \lt 1, 2a-1 \lt b \lt \frac{a}{2}+\frac{1}{2}$, and the probability is $\frac{1}{2}$.
- $(0,2)$: The necessary and sufficient condition for it to be contained in the interior of $Q$ is $0 \lt a \lt \frac{b}{2} \lt 1$, and the probability is $\frac{1}{4}$.
- $(1,1)$: The necessary and sufficient condition for it to be contained in the interior of $Q$ is $0 \lt b \lt \frac{a}{2} \lt 1$, and the probability is $\frac{1}{4}$.
- $(1,2)$: The necessary and sufficient condition for it to be contained in the interior of $Q$ is $0 \lt a, b \lt 1, 1 \lt a+b$, and the probability is $\frac{1}{2}$.
From the above, the expected number of lattice points contained in the interior of $Q$ is $\frac{3}{2}$. Since $2 \times 499122178 \equiv 3 \pmod{998244353}$, output $499122178$.
Sample 2
Input
13 541787 -802804 745984 -610628 821010 -469321 148557 920322 -276352 776016 -689247 481241 -955894 130548 -804935 -349606 -374167 -778760 -33915 -920255 5303 -921478 231589 -902268 348969 -873524
Output
68155167
The polygon $P$ is as follows:
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