- 题目提供者 FarmerJohn2
- 评测方式 云端评测
- 标签 USACO 2015 高性能
- 难度 提高+/省选-
- 时空限制 1000ms / 128MB
For Bessie the cow’s birthday, Farmer John has given her free reign over one
of his best fields to eat grass.
The field is covered in $N$ patches of grass ($1 \le N \le 1000$), conveniently
numbered $1\ldots N$, that each have a distinct quality value. If Bessie eats
grass of quality $Q$, she gains $Q$ units of energy. Each patch is connected to
up to 10 neighboring patches via bi-directional paths, and it takes Bessie $E$
units of energy to move between adjacent patches ($1 \le E \le 1,000,000$).
Bessie can choose to start grazing in any patch she wishes, and she wants to
stop grazing once she has accumulated a maximum amount of energy.
Unfortunately, Bessie is a picky bovine, and once she eats grass of a certain
quality, she’ll never eat grass at or below that quality level again! She is
still happy to walk through patches without eating their grass; in fact, she
might find it beneficial to walk through a patch of high-quality grass without
eating it, only to return later for a tasty snack.
Please help determine the maximum amount of energy Bessie can accumulate.
The first line of input contains $N$ and $E$. Each of the remaining $N$ lines
describe a patch of grass. They contain two integers $Q$ and $D$ giving the
quality of the patch (in the range $1\ldots 1,000,000$) and its number of
neighbors. The remaining $D$ numbers on the line specify the neighbors.
Please output the maximum amount of energy Bessie can accumulate.
Bessie starts at patch 4 gaining 5 units of energy from the grass there. She
then takes the path to patch 5 losing 2 units of energy during her travel.
She refuses to eat the lower quality grass at patch 5 and travels to patch 3
again losing 2 units of energy. Finally she eats the grass at patch 3 gaining 6 units of energy
for a total of 7 energy.
Note tha the sample case above is different from test case 1 when you submit.