题目描述 "But baby, I've been, I've been praying hard,     Said, no more counting dollars     We'll be counting stars" Grandpa Shaw loves counting stars. One evening he was sitting in his armchar, trying to figure out this problem. Consider the sky…

Counting Stars 题目链接:http://acm.xidian.edu.cn/problem.php?id=1177 离线+一维树状数组 一眼扫过去:平面区间求和,1e6的数据范围,这要hash+二维树状数组吧?这么短时间我肯定调不出来,果断弃... 结束后有人说一维树状数组可以做,ヾ(｡｀Д´｡)离线啊没想到. 然后就成了水题...(坐标要++,因为是从零开始的) 感悟:离线算法在某种情况下可以降低复杂度的维度. 代码如下: #include<cstdio> #include&l…

Problem Description Little A is an astronomy lover, and he has found that the sky was so beautiful!So he is counting stars now!There are n stars in the sky, and little A has connected them by m non-directional edges.It is guranteed that no edges conn…

Problem Description Little A is an astronomy lover, and he has found that the sky was so beautiful! So he is counting stars now! There are n stars in the sky, and little A has connected them by m non-directional edges. It is guranteed that no edges c…

hdu 6184 Counting Stars(三元环计数) 题意: 给一张n个点m条边的无向图,问有多少个\(A-structure\) 其中\(A-structure\)满足\(V=(A,B,C,D)\) && \(E=(AB,BC,CD,DA,AC)\) 显然\(A-structure\)是由两个有公共边的三元环构成的 \(1 <=n <= 1e5\) \(1 <= m <= min(2e5,n*(n-1)/2)\) 思路: 三元环计数 做法1. ①统计每个点…

题目链接:http://acm.hdu.edu.cn/showproblem.php?pid=6184 题意: n个点m条边的无向图,问有多少个A-structure 其中A-structure满足V=(A,B,C,D) && E=(AB,BC,CD,DA,AC) 解法: 可以看出A-structure是由两个有公共边的三元环构成的,然后就变成了这道题. http://www.cnblogs.com/spfa/p/7495438.html #include <stdio.h>…

题面 传送门 给出一张无向图,求 \(4\) 个点构成两个有公共边的三元环的方案数. 题解 orz余奶奶,orz zzk 首先,如果我们知道经过每条边的三元环个数\(cnt_i\),那么答案就是\(\sum_{i=1}^m{cnt_i\choose 2}\) 所以现在问题就是该怎么数三元环 据说有一个设阈值的\(O(m\sqrt{m})\)的做法,不过常数太大了,这里不讲 我们把每一条边重定向,设它连接的两个点的度数分别为\(deg_u\)和\(deg_v\),那么把这条边定为从度数大的连向度数…

题目链接 hdu6184 题解 题意是让我们找出所有的这样的图形: 我们只需要求出每条边分别在多少个三元环中,记为\(x\),再然后以该点为中心的图形数就是\({x \choose 2}\) 所以我们只需找出所有三元环 据说这是一个套路题 我们将所有无向边改为有向边,由度数小的向度数大的连边,度数相同就由编号小的向编号大的 容易发现这样建图一定是一个\(DAG\) 然后我们枚举边,将边的两端点出边的到达的点打上标记,当一个点被打上同一个标记时,就成环了 因为是\(DAG\)容易发现这样找环不会重…

1.Sign 题目:Good Luck!flag{X-nuca@GoodLuck!} Flag直接写在题目上了,flag{X-nuca@GoodLuck!} 2.BaseCoding 提示:这是编码不是加密哦!一般什么编码里常见等号? 题目:这一串字符好奇怪的样子,里面会不会隐藏什么信息?http://question1.erangelab.com/ Base64-- 访问后得到一串含有等号的字符,然后base64解码得到flag 3.BaseInjection 提示:试试万能密码 题目:不知道…

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