| 题目名称 | 770. [USACO Open09] Tied Down |
|---|---|
| 输入输出 | tied.in/out |
| 难度等级 | ★ |
| 时间限制 | 1000 ms (1 s) |
| 内存限制 | 128 MiB |
| 测试数据 | 11 |
| 题目来源 |
 Makazeu
于2012-04-16加入 |
| 开放分组 | 全部用户 |
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Problem 1: Tied Down [Brian Dean, 2012]
As we all know, Bessie the cow likes nothing more than causing mischief on
the farm. To keep her from causing too much trouble, Farmer John decides
to tie Bessie down to a fence with a long rope. When viewed from above,
the fence consists of N posts (1 <= N <= 10) that are arranged along
vertical line, with Bessie's position (bx, by) located to the right of this
vertical line. The rope FJ uses to tie down Bessie is described by a
sequence of M line segments (3 <= M <= 10,000), where the first segment
starts at Bessie's position and the last ends at Bessie's position. No
fence post lies on any of these line segments. However, line segments may
cross, and multiple line segments may overlap at their endpoints.
Here is an example of the scene, viewed from above:
To help Bessie escape, the rest of the cows have stolen a saw from the barn. Please determine the minimum number of fence posts they must cut through and remove in order for Bessie to be able to pull free (meaning she can run away to the right without the rope catching on any of the fence posts). All (x,y) coordinates in the input (fence posts, Bessie, and line segment endpoints) lie in the range 0..10,000. All fence posts have the same x coordinate, and bx is larger than this value. PROBLEM NAME: tied INPUT FORMAT: * Line 1: Four space-separated integers: N, M, bx, by. * Lines 2..1+N: Line i+1 contains the space-separated x and y coordinates of fence post i. * Lines 2+N..2+N+M: Each of these M+1 lines contains, in sequence, the space-separated x and y coordinates of a point along the rope. The first and last points are always the same as Bessie's location (bx, by). SAMPLE INPUT (file tied.in): 2 10 6 1 2 3 2 1 6 1 2 4 1 1 2 0 3 1 1 3 5 4 3 0 0 1 3 2 6 1 INPUT DETAILS: There are two posts at (2,3) and (2,1). Bessie is at (6,1). The rope goes from (6,1) to (2,4) to (1,1), and so on, ending finally at (6,1). The shape of the rope is the same as in the figure above. OUTPUT FORMAT: * Line 1: The minimum number of posts that need to be removed in order for Bessie to escape by running to the right. SAMPLE OUTPUT (file tied.out): 1 OUTPUT DETAILS: Removing either post 1 or post 2 will allow Bessie to escape.
barn. Please determine the minimum number of fence posts they must cut through and remove in order for Bessie to be able to pull free (meaning she can run away to the right without the rope catching on any of the fence posts). All (x,y) coordinates in the input (fence posts, Bessie, and line segment endpoints) lie in the range 0..10,000. All fence posts have the same x coordinate, and bx is larger than this value. PROBLEM NAME: tied INPUT FORMAT: * Line 1: Four space-separated integers: N, M, bx, by. * Lines 2..1+N: Line i+1 contains the space-separated x and y coordinates of fence post i. * Lines 2+N..2+N+M: Each of these M+1 lines contains, in sequence, the space-separated x and y coordinates of a point along the rope. The first and last points are always the same as Bessie's location (bx, by). SAMPLE INPUT (file tied.in): 2 10 6 1 2 3 2 1 6 1 2 4 1 1 2 0 3 1 1 3 5 4 3 0 0 1 3 2 6 1 INPUT DETAILS: There are two posts at (2,3) and (2,1). Bessie is at (6,1). The rope goes from (6,1) to (2,4) to (1,1), and so on, ending finally at (6,1). The shape of the rope is the same as in the figure above. OUTPUT FORMAT: * Line 1: The minimum number of posts that need to be removed in order for Bessie to escape by running to the right. SAMPLE OUTPUT (file tied.out): 1 OUTPUT DETAILS: Removing either post 1 or post 2 will allow Bessie to escape.