HackerRank training-the-army

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HackerRank "Training the army" - Max Flow

First problem to learn Max Flow. Ford-Fulkerson is a group of algorithms - Dinic is one of it.It is an iterative process: we use BFS to check augament-ability, and use DFS to augment it. Here is the code with my comments from its tutorial #include <c…

2019 Multi-University Training Contest 2 - 1008 - Harmonious Army - 最大流

http://acm.hdu.edu.cn/showproblem.php?pid=6598 一开始就觉得是网络流,但是一直都不会怎么建图. 这里要考虑. 每一组边(u,v,a,b,c)建立如下的连接: (s,u,a),(s,v,a),(u,t,c),(v,t,c),(u,v,a+c-2b) 这样,看看,每次最小割把这个切断的时候,要么切断2a,使得u,v同属于t,要么切断2c,使得u,v同属于s.再或者,斜着切断三条边,合计2a+2c-2b. 那么假如最小割的值是sum,那么 (a+c)-su…

2019 Multi-University Training Contest 2 Harmonious Army(最小割)

题意:给你n个点每个点都有两种选择成为战士或者法师现在给你m个关系对应这两个人的对应关系的权值A,B,C 思路:按照下面的思路建图跑最小割(要注意权值要乘2 可能存在不整除的情况) #include <bits/stdc++.h> using namespace std; const double pi = acos(-1.0); const int maxn = 1e3+7; const int inf = 0x3f3f3f3f; const double eps = 1e-6; t…

Gym - 100283F F. Bakkar In The Army —— 二分

题目链接:http://codeforces.com/gym/100283/problem/F F. Bakkar In The Army time limit per test 2 seconds memory limit per test 256 megabytes input army.in output standard output Bakkar is now a senior college student studying computer science. And as many…

2019 Multi-University Training Contest 2

2019 Multi-University Training Contest 2 A. Another Chess Problem B. Beauty Of Unimodal Sequence 题意给一个序列,求下标字典序最小和字典序最大的,先增后减的序列. 解体过程比赛时首先不知道字典序最小LIS怎么求. 试图枚举分界点.[解体的开始] 公无渡河,公竟渡河? 活鱼在摸鱼,rdc在划水,sdcgvhgj在水深火热. 做法考虑字典序最小的LIS怎么求? 这是个经典问题,预处理前缀LIS后缀L…

HDU校赛 | 2019 Multi-University Training Contest 2

2019 Multi-University Training Contest 2 http://acm.hdu.edu.cn/contests/contest_show.php?cid=849 1005. Everything Is Generated In Equal Probability 考虑一个随机的排列的逆序对个数,显然对于两个数\(a,b\),他们位置是均匀排布的,也就是说有\(\frac{1}{2}\)的概率成为逆序对,并且是独立的. 所以一个长度为\(n\)的随机排列期望逆序对个…