poj 1113 Wall (凸包模板题）

Max Angle # **Time Limit: 4000/2000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others) Total Submission(s): 678 Accepted Submission(s): 238 ** Problem Description Given many points in a plane, two players are playing an interesting game. Player1 selects one point A as the vertex of an angle. Then player2 selects other two points B and C. A, B and C are different with each other. Now they get an angle B-A-C.

Transmitters Time Limit: 1000MS Memory Limit: 10000K Total Submissions: 4817 Accepted: 2576 Description In a wireless network with multiple transmitters sending on the same frequencies, it is often a requirement that signals don’t overlap, or at least that they don’t conflict. One way of accomplishing this is to restrict a transmitter’s coverage area. This problem uses a shielded transmitter that only broadcasts in a semicircle. A transmitter T is located somewhere on a 1,000 square meter grid. It broadcasts in a semicircular area of radius r. The transmitter may be rotated any amount, but not moved. Given N points anywhere on the grid, compute the maximum number of points that can be simultaneously reached by the transmitter’s signal. Figure 1 shows the same data points with two different transmitter rotations.

20190211update：工作的时候看同事ocr的代码，发现有一段就是极角排序orz…所以说算法还是有用的… 先介绍几种极角排序： 1.利用叉积的正负来作cmp.(即是按逆时针排序).此题就是用这种方法