Problem E
Cursed Vault
H’Arrry, Rrron, and Anemone have found a vault of treasure! But unfortunately for them, the vault is cursed. Once they open the vault, the vault begins duplicating the treasure held within over the course of $T$ time steps.
Specifically, the vault is separated into $N$ locations $0, 1 , \dots , n-1$, each location starting with $1$ treasure in it at $t=0$ when the vault is opened. Each location is also connected to some number of other locations.
The vault will duplicate treasure over $T$ time steps (until $t = T$), and treasure in different locations are duplicated in different ways.
After each time step $t$, each location $i$ will add treasure at the next time step in one of two ways:
-
Adds a single treasure to every location it’s connected to.
-
Adds $k_{i, t}$ treasure to every location it’s connected to where $k_{i, t}$ is the current amount of treasure in the location.
Locations do not add treasure to themselves, and the amount of treasure to be added at the next time step $t+1$ is determined by the amount of treasure in the location at the current time step $t$.
Calculate the sum of all treasure contained in all locations in the vault at time $t = T$ (where $T$ time steps have passed). Because this number may be very large, output the answer modulo $10^9 + 7$.
Input
The first line of input contains three integers $N$, $M$, and $T$ ($2
\leq N \leq 50$, $1 \leq M
\leq \frac{N(N-1)}{2}$, $1
\leq T \leq 10^{12}$), the number of locations, the
number of connections, and the number of time steps.
The next $N$ lines each
contain a single integer 1 or 2, where the $i$th line indicates the way that
$i-1$th location
duplicates treasure (either the 1st way or the 2nd way).
The next $M$ lines each
contain two integers $u$
and $v$ ($0 \leq u, v \leq N-1$, $u < v$), indicating that location
$u$ is connected to
location $v$ and location
$v$ is connected to
location $u$. The same
connection will not appear twice in the input.
Output
Output the total amount of treasure in the vault after $T$ time steps, modulo $10^9 + 7$.
Sample Input 1 | Sample Output 1 |
---|---|
2 1 2 1 2 0 1 |
7 |
Sample Input 2 | Sample Output 2 |
---|---|
4 4 3 1 2 2 1 0 1 1 2 2 3 1 3 |
79 |