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…

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…

      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…

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)…

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…

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…

题意:给你a, b, c, d四个数,这几个数的范围都是大于0小于1000的整数,让比较 a ^b 和 c ^ d的大小. 这道题看着特别简单,但是当时就是做不出来,将近一个月没有做题了,手生了,不过看完题解之后,这个题还是挺简单的,关键就是一步转化就是两边同时取对数也就成为了b * log(a) 与 d * log(c)的大小比较,所以这样的话就在double的范围内了,不过还需注意一点就是有误差,不能完全正确的,因为在取对数的时候有个误差,所以要设置一个精度,代码如下: #include <…

题目链接:Inversion Counting 题意: 定义数列{ai|i=1,2,...,n}的逆序对如下:对于所有的1≤j<i≤n,若ai<aj,则<i,j>为一个逆序对.于是,对于一个数列a[1..n],给定m次操作.对于每一次操作,给定l,r(1≤l<r≤n),将序列a[l..r]倒置.求倒置后的逆序对的数量的奇偶性. 题解: 假设现在我们有一个序列并翻转这个序列[l,r]区间里面的数.假设某个数的k值是指在这个值后面小于这个数的数的个数,其实我们可以发现对于[1,l…

Number of Parallelograms time limit per test 4 seconds memory limit per test 256 megabytes input standard input output standard output You are given n points on a plane. All the points are distinct and no three of them lie on the same line. Find the…