题意 题目链接 Sol 树上差分模板题 发现自己傻傻的分不清边差分和点差分 边差分就是对边进行操作,我们在\(u, v\)除加上\(val\),同时在\(lca\)处减去\(2 * val\) 点差分是对点操作,我们在\(u, v\)处加上\(val\),在\(lca\)和\(fa[lca]\)处减去\(val\) 就本题而言,属于点差分 #include<bits/stdc++.h> const int MAXN = 1e5 + 10; using namespace std; inline…

题目:https://www.luogu.org/problemnew/show/P3128 树上差分.用离线lca,邻接表存好方便. #include<iostream> #include<cstdio> #include<cstring> #include<algorithm> using namespace std; ,M=1e5+; ],nxt[M<<],ans; bool vis[N]; struct Ed{ ,):nxt(n),to(…

题目描述 Farmer John has installed a new system of N-1N−1 pipes to transport milk between the NN stalls in his barn (2 \leq N \leq 50,0002≤N≤50,000), conveniently numbered 1 \ldots N1-N. Each pipe connects a pair of stalls, and all stalls are connected t…

题目:https://www.luogu.org/problemnew/show/P3128 倍增求 lca 也写错了活该第一次惨WA. 代码如下: #include<iostream> #include<cstdio> #include<cstring> #include<algorithm> using namespace std; ; ],dep[maxn],s[maxn],mx; bool vis[maxn]; struct N{ int to,nx…

链接一下题目:luoguP3128 [USACO15DEC]最大流Max Flow(树上差分板子题) 如果没有学过树上差分,抠这里(其实很简单的,真的):树上差分总结 学了树上差分,这道题就极其显然了,不就是把每一条运输路线差分进去,那就是板子了啊. 树上差分还是很有用的,比较容易写,这种询问很少的题目去敲那么长(还容易出玄学错误)的树剖很浪费,用树上差分就很快了!(//...微笑...\\) 上一波代码: #include<iostream> #include<cstdlib>…

跟LOJ10131暗的连锁 相似,只是对于\(lca\)节点把它和父亲减一 #include <cstdio> #include <iostream> #include <cstring> #include <algorithm> #include <cmath> #define R(a,b,c) for(register int a = (b); (a) <= (c); ++(a)) #define nR(a,b,c) for(regis…

因为徐州现场赛的G是树上差分+组合数学,但是比赛的时候没有写出来(自闭),背锅. 会差分数组但是不会树上差分,然后就学了一下. 看了一些东西之后,对树上差分写一点个人的理解: 首先要知道在树上,两点之间只有一条路径.树上差分就是在树上用差分数组,因为是在树上的操作,所以要用到lca,因为对于两点a,b,从a到b这一条链就是a-->lca(a,b)-->b,这是一条链. 其次,树上差分的两种操作:一种是对点权的,另一种是对边权的. 对于点权: 在树上将路径的起点a+1和终点b+1,lca(a,b…

P3128 [USACO15DEC]最大流Max Flow 题目描述 Farmer John has installed a new system of  pipes to transport milk between the  stalls in his barn (), conveniently numbered . Each pipe connects a pair of stalls, and all stalls are connected to each-other via path…

P3128 [USACO15DEC]最大流Max Flow 题目描述 Farmer John has installed a new system of N-1N−1 pipes to transport milk between the NN stalls in his barn (2 \leq N \leq 50,0002≤N≤50,000), conveniently numbered 1 \ldots N1…N. Each pipe connects a pair of stalls,…

#\(\mathcal{\color{red}{Description}}\) \(Link\) \(FJ\)给他的牛棚的\(N(2≤N≤50,000)\)个隔间之间安装了\(N-1\)根管道,隔间编号从\(1\)到\(N\).所有隔间都被管道连通了. \(FJ\)有\(K(1≤K≤100,000)\)条运输牛奶的路线,第i条路线从隔间\(s_i\)运输到隔间\(t_i\).一条运输路线会给它的两个端点处的隔间以及中间途径的所有隔间带来一个单位的运输压力,你需要计算压力最大的隔间的压力是多少.…