凸包算法讲解:Click Here 题目链接:https://vjudge.net/problem/POJ-1113 题意:简化下题意即求凸包的周长+2×PI×r. 思路:用graham求凸包,模板是kuangbin的,算法复杂度O(nlogn). AC code: // Author : RioTian // Time : 20/10/21 #include <algorithm> #include <cmath> #include <cstdio> #include…
凸包模板--Graham扫描法 First 标签: 数学方法--计算几何 题目:洛谷P2742[模板]二维凸包/[USACO5.1]圈奶牛Fencing the Cows yyb的讲解:https://www.cnblogs.com/cjyyb/p/7260523.html 模板 #include<iostream> #include<cstdlib> #include<cstdio> #include<cmath> #include<cstring&…
凸包的概念 首先,引入凸包的概念: (有点窄的时候...图片右边可能会被吞,拉开图片看就可以了) 大概长这个样子: 那么,给定一些散点,如何快速地求出凸包呢(用在凸包上的点来表示凸包) Andrew算法流程和思想 常见的求凸包的算法有$Graham$和$Andrew$,$Andrew$是$Graham$扫描算法的变种,和$Graham$相比,$Andrew$更快,且更稳定,所以主要讲一下$Andrew$. 首先把所有点以$x$坐标为第一关键字,$y$坐标为第二关键字从小到大进行排序,可以肯定第一…
题目链接 /* Name:nyoj-78-圈水池 Copyright: Author: Date: 2018/4/27 9:52:48 Description: Graham求凸包 zyj大佬的模板,改个输出就能用 */ #include <cstring> #include <iostream> #include <cstdio> #include <algorithm> using namespace std; struct point{ double…
#include<iostream> #include<cstdio> #include<cmath> #include<vector> #include<algorithm> using namespace std; struct Point { int x, y; Point(int x=0, int y=0):x(x),y(y) { } }; typedef Point Vector; Vector operator - (const Po…
Description Once upon a time there was a greedy King who ordered his chief Architect to build a wall around the King's castle. The King was so greedy, that he would not listen to his Architect's proposals to build a beautiful brick wall with a perfec…
链接: http://poj.org/problem?id=2187 http://acm.hust.edu.cn/vjudge/contest/view.action?cid=22013#problem/E Beauty Contest Time Limit: 3000MS   Memory Limit: 65536K Total Submissions: 24254   Accepted: 7403 Description Bessie, Farmer John's prize cow, h…
凸包 (只针对二维平面内的凸包) 一.定义 简单的说,在一个二维平面内有n个点的集合S,现在要你选择一个点集C,C中的点构成一个凸多边形G,使得S集合的所有点要么在G内,要么在G上,并且保证这个凸多边形的面积最小,我们要求的就是这个C集合. 二.算法 求凸包的算法很多,常用的有两种: 1.  Graham扫描法,运行时间为O(nlgn). 2.  Jarvis步进法,运行时间为O(nh),h为凸包中的顶点数. 这里主要讨论第一种算法:Graham扫描法 Graham扫描法: 基本思想:使用一个栈…
Cows Time Limit: 2000MS   Memory Limit: 65536K Total Submissions: 6199   Accepted: 2822 Description Your friend to the south is interested in building fences and turning plowshares into swords. In order to help with his overseas adventure, they are f…
题目链接:https://vjudge.net/problem/POJ-1113 题意:简化下题意即求凸包的周长+2×PI×r. 思路:用graham求凸包,模板是kuangbin的. AC code: #include<cstdio> #include<cstring> #include<algorithm> #include<cmath> using namespace std; ; const double PI=acos(-1.0); struct…