1058 - Parallelogram Counting There are n distinct points in the plane, given by their integer coordinates. Find the number of parallelograms whose vertices lie on these points. In other words, find the number of 4-element subsets of these points tha…

链接: https://vjudge.net/problem/LightOJ-1058 题意: There are n distinct points in the plane, given by their integer coordinates. Find the number of parallelograms whose vertices lie on these points. In other words, find the number of 4-element subsets o…

Description There are n distinct points in the plane, given by their integer coordinates. Find the number of parallelograms whose vertices lie on these points. In other words, find the number of 4-element subsets of these points that can be written a…

http://www.lightoj.com/volume_showproblem.php?problem=1058 题意:给你顶点,问能够成多少个平行四边形. 思路:开始想使用长度来扫描有多少根,但是好像坐标太大似乎不可行.其实我们可以通过找所有线段的中点的重合个数来计算有几个平行四边形,这种通过别的性质来判断几何关系的思维是解几何题的基础,当作入门? /** @Date : 2016-12-02-21.49 * @Author : Lweleth (SoungEarlf@gmail.com)…

1058 - Parallelogram Counting    PDF (English) Statistics Forum Time Limit: 2 second(s) Memory Limit: 32 MB There are n distinct points in the plane, given by their integer coordinates. Find the number of parallelograms whose vertices lie on these po…

Parallelogram Counting Time Limit: 5000MS   Memory Limit: 65536K Total Submissions: 5749   Accepted: 1934 Description There are n distinct points in the plane, given by their integer coordinates. Find the number of parallelograms whose vertices lie o…

      Parallelogram Counting Time Limit: 5000MS   Memory Limit: 65536K Total Submissions: 6895   Accepted: 2423 Description There are n distinct points in the plane, given by their integer coordinates. Find the number of parallelograms whose vertices…

题目链接: http://poj.org/problem?id=1971 题意: 二维空间给n个任意三点不共线的坐标,问这些点能够组成多少个不同的平行四边形. 题解: 使用的平行四边形的判断条件:对角线互相平分的四边形是平行四边形. 所以我们枚举每一条线段,如果有两条线段的中点是重合的,那么这四个顶点就能构成一个平行四边形,也就是说每条线段我们只要维护中点就可以了. 1.map维护中点:(数据比较大,t了) #include<iostream> #include<cstdio> #…

Description There are n distinct points in the plane, given by their integer coordinates. Find the number of parallelograms whose vertices lie on these points. In other words, find the number of 4-element subsets of these points that can be written a…

Parallelogram Counting 刚学hash还不会用,看到5000ms的时限于是想着暴力来一发应该可以过.以前做过类似的题,求平行四边形个数,好像是在CF上做的,但忘了时限是多少了,方法是一样的. 题意:给出n个点坐标,求平面中有多少个平行四边形. 思路:我们知道,平行四边形的条件是两条边平行且相等.我们把每条边分解成x和y方向的向量,只要两条边对应相等就可以了,于是预处理所有的边,然后排序,然后相等的肯定在一起,所以用试探法往前,注意每个平形四边形都被记录了两次,所以答案是总数量…

http://codeforces.com/problemset/problem/749/B 题意:已知平行四边形三个顶点,求另外一个顶点可能的位置. 思路:用向量来做. #include <cstdio> #include <algorithm> #include <iostream> #include <cstring> #include <string> #include <cmath> #include <queue&g…

极角排序后枚举每个点,计算其与原点连线的左侧的半平面内的点与其组成的三角形数(二分/尺取),这些都不是黄金三角形. 补集转化,用平面内所有三角形的个数(C(n,3))减去这些即可. 精度很宽松,几乎不用管. #include<cstdio> #include<algorithm> #include<cmath> using namespace std; typedef long long ll; typedef double db; #define N 100001 c…

Higher Math Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)Total Submission(s): 2219    Accepted Submission(s): 1219 Problem Description You are building a house. You’d prefer if all the walls have a precise right…

题目链接:1058. 挤模具 题意 给出模具的底和体积,求模具的高. 思路 模具的底为多边形,因此求出多边形面积,用体积除以底的面积就是答案. 多边形的面积求解见 EOJ 1127. 多边形面积(计算几何) 代码 #include <cstdio> #include <iostream> #include <vector> #include <cmath> #include <algorithm> using namespace std; typ…

在上篇,我了解了基数的基本概念,现在进入Linear Counting算法的学习. 理解颇浅,还请大神指点! http://blog.codinglabs.org/articles/algorithms-for-cardinality-estimation-part-ii.html 它的基本处理方法和上篇中用bitmap统计的方法类似,但是最后要用到一个公式: 说明:m为bitmap总位数,u为0的个数,最后的结果为n的一个估计,且为最大似然估计(MLE). 那么问题来了,最大似然估计是什么东东…

来之不易的2017第一发ac http://poj.org/problem?id=2386 Lake Counting Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 31474   Accepted: 15724 Description Due to recent rains, water has pooled in various places in Farmer John's field, which is repr…

ZOJ3944 People Counting ZOJ3939 The Lucky Week 1.PeopleConting 题意:照片上有很多个人,用矩阵里的字符表示.一个人如下: .O. /|\ (.) 占3*3格子,句号“.”为背景.没有两个人完全重合.有的人被挡住了一部分.问照片上有几个人. 题解: 先弄个常量把3*3人形存起来,然后6个部位依次找,比如现在找头,找到一个头,就把这个人删掉(找这个人的各个部位,如果在该部位位置的不是这个人的身体,就不删),删成句号,疯狂找就行了. 代码:…

POJ2318 本题需要运用to left test不断判断点处于哪个分区,并统计分区的点个数(保证点不在边界和界外),用来做叉积入门题很合适 //计算几何-叉积入门题 //Time:157Ms Memory:828K #include<iostream> #include<cstring> #include<cstdio> #include<algorithm> using namespace std; #define MAXN 5005 struct P…

---------------------------------------- 简单搜索+剪枝 因为考虑到可能会有多个解,所以是将中间过程保存最后才一起打印出来的 AC代码: 1: 2: import java.util.ArrayList; 3: import java.util.List; 4: import java.util.Scanner; 5: 6: public class Main { 7: 8: public static void main(String[] args) {…

#include <stdio.h> #include <malloc.h> #define MAX_STACK 10 ; // define the node of stack typedef struct node { int data; node *next; }*Snode; // define the stack typedef struct Stack{ Snode top; Snode bottom; }*NewStack; void creatStack(NewSt…

最大三角形 Time Limit: 5000/2000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)Total Submission(s): 4015    Accepted Submission(s): 1433 Problem Description 老师在计算几何这门课上给Eddy布置了一道题目,题目是这样的:给定二维的平面上n个不同的点,要求在这些点里寻找三个点,使他们构成的三角形拥有的面积最大.Eddy对这道…

http://www.cnblogs.com/acsmile/archive/2011/05/09/2040918.html 计算几何头疼的地方一般在于代码量大和精度问题,代码量问题只要平时注意积累模板一般就不成问题了.精度问题则不好说,有时候一个精度问题就可能成为一道题的瓶颈,简直“画龙点睛”.这些年的题目基本是朝着越来越不卡精度的方向发展了,但是也不乏一些%^&%题#$%$^,另外有些常识不管题目卡不卡,都是应该知道的.今天我就开膛回顾下见过且还有印象的精度问题,由于本人见识和记忆均有限,望…

1004. Counting Leaves (30)   A family hierarchy is usually presented by a pedigree tree. Your job is to count those family members who have no child. Input Each input file contains one test case. Each case starts with a line containing 0 < N < 100,…

Problem Figure 2. The Hamming distance between these two strings is 7. Mismatched symbols are colored red. Given two strings ss and tt of equal length, the Hamming distance between ss and tt, denoted dH(s,t)dH(s,t), is the number of corresponding sym…

Problem A string is simply an ordered collection of symbols selected from some alphabet and formed into a word; the length of a string is the number of symbols that it contains. An example of a length 21 DNA string (whose alphabet contains the symbol…

// uva 11401 Triangle Counting // // 题目大意: // // 求n范围内,任意选三个不同的数,能组成三角形的个数 // // 解题方法: // // 我们设三角巷的最长的长度是c(x),另外两边为y,z // 则由z + y > x得, x - y < z < x 当y = 1时,无解 // 当y = 2时,一个解,这样到y = x - 1 时 有 x - 2个 // 解,所以一共是0,1,2,3....x - 2,一共(x - 2) * (x - 1…

当我们在使用JSONKit处理数据时,直接将文件拉进项目往往会报这两个错“JSONKit   does not support Objective-C Automatic Reference Counting(ARC)”,“ARC forbids Objective-C objects in struct”,这是由于JSONKit库未更新,不支持ARC机制.我们可以参照如下步骤解决:…

有使用JSonKit的朋友,如果遇到“JSonKit does not support Objective-C Automatic Reference Counting(ARC)”这种情况,可参照如下方法: 点击项目根目录->targets->Build Phases->JSONKit.m->添加“-fno-objc-arc”字段,在运行就OK了.…

Lake Counting Time Limit: 1000MS     Memory Limit: 65536K Total Submissions: 17917     Accepted: 9069 Description Due to recent rains, water has pooled in various places in Farmer John's field, which is represented by a rectangle of N x M (1 <= N <=…

题目链接:http://acm.hdu.edu.cn/showproblem.php?pid=1058 解题报告:输入一个n,输出第n个质因子只有2,3,5,7的数. 用了离线打表,因为n最大只有5842. #include<stdio.h> #define INT __int64 INT ans[] = { ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,…