poj 1269 Intersecting Lines (计算几何)

B. Anton and Lines time limit per test 1 second memory limit per test 256 megabytes input standard input output standard output The teacher gave Anton a large geometry homework, but he didn’t do it (as usual) as he participated in a regular round on Codeforces. In the task he was given a set of n lines defined by the equations y = k__i*x + b__i. It was necessary to determine whether there is at least one point of intersection of two of these lines, that lays strictly inside the strip between _x_1 < _x_2. In other words, is it true that there are1 ≤ i < j ≤ n and x’, y’, such that:

题意：给定一个六边形的六条边的长，问能分割成多少个单位正三角形． 分割不好办，那我们就反着来，先补成一个包含这个六边形的正三角形． 对于边长为a的正三角形，显然我们可以分割成a*a个单位正三角形

Collision Detection # **Time Limit: 5000/1000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others) Total Submission(s): 1207 Accepted Submission(s): 367 ** Problem Description In physical simulations, video games and computational geometry, collision detection involves algorithms for checking for collision, i.e. intersection, of two given objects. Collision detection algorithms are a basic component of 3D video games. Without them, characters could go through walls and other obstacles. Here comes an interesting problem, given a ball and a cuboid, you need to detect whether they collide. We say that two objects collide if and only if they share at least one point.

http://acm.hust.edu.cn/vjudge/contest/view.action?cid=83295#problem/I 最多18个点，选3个点，能够成的三角形不超过1000个，O(n2)暴力就可以。 思路就是枚举三个点点，对于每一个构成的三角形，把这个三角形的最小角和次小角存起来。 然后枚举三角形，判断是否有两个三角形的最小角和次小角分别对应相等。

http://poj.org/problem?id=2398 题意大概是说将一个盒子用n个board分成n+1 部分 然后往里面放toy，给定盒子，board，和toy的坐标 问所有的toy放完后，有多少部分中有t个toy; 简单计算几何