[科普]什么是BestCoder?如何参加? Surround the Trees Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others) Total Submission(s): 8113    Accepted Submission(s): 3095 Problem Description There are a lot of trees in an area. A peasant…

Surround the Trees 此题讨论区里大喊有坑,原谅我没有仔细读题还跳过了坑点. 题意:平面上有n棵树,选一些树用绳子围成一个包围圈,使得所有的树都在这个圈内. 思路:简单凸包入门题,凸包裸模板.在做这个题前建议先去学学:叉积,极角排序,三角形有向面积. 贴上代码以后再复习. struct node { double x,y; } a[N],p[N]; int n,tot;//总点数和凸包上的点数: double dis(node a,node b)//两点间距离 { return…

Description There are a lot of trees in an area. A peasant wants to buy a rope to surround all these trees. So at first he must know the minimal required length of the rope. However, he does not know how to calculate it. Can you help him?        The…

Wall Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others) Total Submission(s): 3779    Accepted Submission(s): 1066 Problem Description Once upon a time there was a greedy King who ordered his chief Architect to build a…

第一次做凸包,这道题要特殊考虑下,n=2时的情况,要除以二才行. 我是从最左边的点出发,每次取斜率最大的点,一直到最右边的点. 然后从最左边的点出发,每次取斜率最低的点,一直到最右边的点. #include<stdio.h> #include<math.h> #include<algorithm> #include<string.h> using namespace std; const double eps=1e-9; struct node { doub…

思路: 凸包模板题. 注意n=1和n=2的情况. 当n=1时,不需要绳子. 当n=2时,绳子长度为两棵树之间距离. 当n≥e时,Graham求凸包即可.最后将凸包上的所有相邻点距离求和. #include<cmath> #include<cstdio> #include<cctype> #include<algorithm> inline int getint() { char ch; while(!isdigit(ch=getchar())); '; )+…

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…

Surround the Trees Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)Total Submission(s): 6812    Accepted Submission(s): 2594 Problem Description There are a lot of trees in an area. A peasant wants to buy a rope to…

Surround the Trees Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others) Total Submission(s): 7164    Accepted Submission(s): 2738 Problem Description There are a lot of trees in an area. A peasant wants to buy a rope to…

Surround the Trees Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others) Total Submission(s): 10803    Accepted Submission(s): 4187 Problem Description There are a lot of trees in an area. A peasant wants to buy a rope t…