题意: 给你一棵有n个节点的树,树的边权都是1. 有m次询问,每次询问输出树上所有节点离其较近结点距离的最大值. 思路: 1.首先是按照常规树形dp的思路维护一个子树节点中距离该点的最大值son_dis[i],维护非子树节点中距离该点的最大值fa_dis[i]; 2.对于每个节点维护它最大的三个儿子节点的son_dis; 3.维护up[i][j]和down[i][j]数组,这个类似倍增lca里边的fa[i][j],up[i][j]代表的含义是从第j个点向上到它的第2^i个父节点这条链上的点除了该…

目录 @description@ @solution@ @accepted code@ @details@ @description@ n 个点连成一棵树,经过每条边需要花费 1 个单位时间. 现给出 m 次询问,每次询问给出两个点,需要求所有点同时出发,最终所有点到达这两个点之一的最小花费时间. input 第一行包含一个整数 n (2 ≤ n ≤ 100000) ,表示点数. 接下来 n-1 行每行两个 1~n 的整数,描述一条边. 接下来包含一个整数 m,表示询问数. 接下来 m 行每行两…

大意: 给定n结点树, m个询问, 每次给出两个旅馆的位置, 求树上所有结点到最近旅馆距离的最大值 先考虑一些简单情形. 若旅馆只有一个的话, 显然到旅馆最远的点是直径端点之一 若树为链的话, 显然是直径端点或两旅馆的中点 这样的话思路就来了, 也就是说最远点要么是直径端点, 要么是到两旅馆距离差不超过1的点 实际求的时候并不需要求出具体在那个点取得最大, 只需简单分类讨论一下, 用RMQ预处理一下, O(1)回答询问 #include <iostream> #include <algo…

题目链接: B. Problems for Round time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output There are n problems prepared for the next Codeforces round. They are arranged in ascending order by their diffi…

题目传送门:http://codeforces.com/problemset/problem/418/D 大意:给出一棵有$N$个节点的树,所有树边边权为$1$,给出$M$次询问,每个询问给出$x,y$两个节点,求$max_{i=1}^N\{min\{dis_{i,x},dis_{i,y}\}\}$.$N,M \leq 10^5$ 倍增+长链剖分这种东西才不会写$qwq$所以写个思维难度大一点的直径写法. 我们考虑将一条直径拎出来,这样就相当于链上挂了若干棵树.因为树的直径有一个很好的性质:树上…

传送门 题意,给一棵树,每次给两个点\(x,y\),求\(\max_{i=1}^{n}(\min(di_{x,i},di_{y,i}))\) 看std看了好久 以下是一个优秀的在线做法,\(O(nlogn)\)预处理,每次询问可以做到\(O(1)\) 首先把直径扣出来,然后就可以把整棵树看成一条直径上挂了n棵树,预处理每个点到直径的最短距离,和直径上每个点挂的树中距离这个点最远的距离\(d_i\) 对于每次询问,造成答案的点要么是直径的端点,要么是两个点路径上的某个直径点挂的树的最远距离的点,于…

题目 题目大意 给你一棵树,然后有一堆询问,每次给出两个点. 问所有点到两个点中最近点的距离的最大值. 正解 本来打了倍增,然后爆了,也懒得调-- 显然可以在两个点之间的路径的中点处割开,一边归一个点管. 有个比较显然的思路是DP,设\(f_x\)表示\(x\)子树内的最远点,\(g_x\)向父亲那边走的最远点. 然后就可以倍增搞,合并一下-- 代码复杂度极高. 然后有个简单又自然的思路是直接打\(LCT\).直接把中间那条边断掉,然后求最远点即可. 想法倒是简单自然,接下来的问题就是,如何求最…

B. Problems for Round 题目连接: http://www.codeforces.com/contest/673/problem/B Description There are n problems prepared for the next Codeforces round. They are arranged in ascending order by their difficulty, and no two problems have the same difficult…

题目链接:http://codeforces.com/contest/727/problem/F 题目大意:有n个问题,每个问题有一个价值ai,一开始的心情值为q,每当读到一个问题时,心情值将会加上该问题的价值.问题只能按顺序读.有m个询问,求当q=bi时,至少要删去多少个问题才能使得在任何时候心情值都>=0 参考这篇:http://blog.csdn.net/aufeas/article/details/53031439 解法一: 贪心 分别求出最多删去i个问题需要的初始心情值的最小值f[i]…

913D - Too Easy Problems 思路:二分check k 代码: #include<bits/stdc++.h> using namespace std; #define ll long long #define pb push_back #define mem(a,b) memset(a,b,sizeof(a)) ; struct pro{ int t,a,id; bool operator < (pro tmp){ return t<tmp.t; } }a[N…

一 题面 D. N Problems During K Days 二 分析 对于这题,刚开始我就是陷入了对公式的执着,企图用公式直接确定第一个数,然后试着去找序列.经过思考和手动模拟后发现是很难保证正确性的. 对于这题,第一步是很明确的,就是确定第一个数,如果给定了$N$和$K$,那么第一个数是可以确定的.因为如果我们只保证后一个数比当前数多1,并且确定第一个数是1,那么可以根据$K$确定对应的最小和$sum$ $sum = \frac{K(K+1)}{2}$ 这个公式应该比较基础.这样我们就可…

[题目]D. Too Easy Problems [题意]给定n个问题和总时限T,每个问题给定时间ti和限制ai,当解决的问题数k<=ai时问题有效,求在时限T内选择一些问题解决的最大有效问题数.n<=2*10^5,T<=10^9. [算法]贪心(排序+堆) [题解]因为T太大,不能考虑背包. 容易发现k越小越能使更多问题有效,所以一定有最优方案的所有问题均有效. 当k唯一确定时,其实就是在所有ai>=k的问题中选取时间最少的几个解决. 当k减小时,选择的范围扩大,就可以选择一些时…

题目描述: time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output You are preparing for an exam on scheduling theory. The exam will last for exactly T milliseconds and will consist of n problems. You…

B: 思路: 暴力,每两个判断一下; C: 思路: 容斥定理,先枚举脖子下面那个点和那个不可描述的点,算出所有的方案数,这里面有多的腿当成了脖子或者胳膊的,然后就再枚举这种情况把这些减去,又减多了; 再把那些两条腿都连在上半身的加上; D: 思路: 分块+前缀和,把sqrt(n)个数字放在一个块里面,预处理块与块之间的贡献,点与块之间的贡献,然后求出前缀和,询问的时候把多余的每凑到一个完整块的拿出来预处理,再把情况分一分就好啦; E: 思路: 水题,随便搞; F: 思路: 二分+前缀和,枚举最后…

Description 有一个长度为 \(n\) 有正负权值的序列,你一开始有一个值,每次到一个权值就加上,最少需要删掉多少数值才能到序列末尾.\(n \leqslant 750,m \leqslant 2 \times 10^5\) Sol DP+二分. 发现这个东西有后效性,就是前面选不选会影响后面的决策,并且权值太大无法记录. 但是我们可以倒着做,因为后面的决策无法影响前面的决策. \(f[i][j]\) 表示到 \(i\) 删掉 \(j\) 个至少需要的初始权值. 因为初始权值非负,所以…

上一次我们拿学校的URP做了个小小的demo.... 其实我们还可以把每个学生的证件照爬下来做成一个证件照校花校草评比 另外也可以写一个物理实验自动选课... 但是出于多种原因,,还是绕开这些敏感话题.. 今天,我们来扒一下cf的题面! PS:本代码不是我原创 1. 必要的分析 1.1 页面的获取 一般情况CF的每一个 contest 是这样的: 对应的URL是:http://codeforces.com/contest/xxx 还有一个Complete problemset页面,它是这样的:…

Codeforces Round #354 (Div. 2) Problems     # Name     A Nicholas and Permutation standard input/output 1 s, 256 MB    x3384 B Pyramid of Glasses standard input/output 1 s, 256 MB    x1462 C Vasya and String standard input/output 1 s, 256 MB    x1393…

Codeforces Round #279 (Div. 2) 做得我都变绿了! Problems     # Name     A Team Olympiad standard input/output 1 s, 256 MB  x2377 B Queue standard input/output 2 s, 256 MB  x1250 C Hacking Cypher standard input/output 1 s, 256 MB  x740 D Chocolate standard in…

http://codeforces.com/contest/489 Problems     # Name     A SwapSort standard input/output 1 s, 256 MB    x2668 B BerSU Ball standard input/output 1 s, 256 MB    x2659 C Given Length and Sum of Digits... standard input/output 1 s, 256 MB    x2261 D U…

http://www.codeforces.com/gym/100827/attachments Hill Number Time Limits:  5000 MS   Memory Limits:  200000 KB 64-bit interger IO format:  %lld   Java class name:  Main Description A Hill Number is a number whose digits possibly rise and then possibl…

Time Limit:2000MS     Memory Limit:262144KB     64bit IO Format:%I64d & %I64u Submit Status Practice CodeForces 519E Description A and B are preparing themselves for programming contests. The University where A and B study is a set of rooms connected…

题目 Source http://codeforces.com/problemset/problem/528/D Description Leonid works for a small and promising start-up that works on decoding the human genome. His duties include solving complex problems of finding certain patterns in long strings cons…

B. Chloe and the sequence 题目链接 http://codeforces.com/contest/743/problem/B 题面 Chloe, the same as Vladik, is a competitive programmer. She didn't have any problems to get to the olympiad like Vladik, but she was confused by the task proposed on the ol…

C. Tennis Championship 题目链接 http://codeforces.com/contest/735/problem/C 题面 Famous Brazil city Rio de Janeiro holds a tennis tournament and Ostap Bender doesn't want to miss this event. There will be n players participating, and the tournament will fo…

http://acm.hust.edu.cn/vjudge/contest/view.action?cid=102271#problem/B Description Kevin Sun has just finished competing in Codeforces Round #334! The round was 120 minutes long and featured five problems with maximum point values of 500, 1000, 1500,…

[codeforces 528]B. Clique Problem 试题描述 The clique problem is one of the most well-known NP-complete problems. Under some simplification it can be formulated as follows. Consider an undirected graph G. It is required to find a subset of vertices C of…

This is the first time I took part in Codeforces Competition.The only felt is that my IQ was contempted.The problem in Div2 was so...em,how to say,anyway I even daren't to believe.Yesterday I solved two fifths of problems.You see? I'm just a guy full…

题目链接: http://codeforces.com/problemset/problem/213/B B. Numbers time limit per test 2 secondsmemory limit per test 256 megabytes 问题描述 Furik loves writing all sorts of problems, especially such that he can't solve himself. You've got one of his proble…

Pythagorean Triples 题目链接: http://codeforces.com/contest/707/problem/C Description Katya studies in a fifth grade. Recently her class studied right triangles and the Pythagorean theorem. It appeared, that there are triples of positive integers such th…

B. HDD is Outdated Technology 题目连接: http://www.codeforces.com/contest/612/problem/B Description HDD hard drives group data by sectors. All files are split to fragments and each of them are written in some sector of hard drive. Note the fragments can…