一个男孩有n只玩具蜘蛛,每只蜘蛛都是一个树的结构,现在男孩准备把这n只小蜘蛛通过粘贴节点接在一起,形成一只大的蜘蛛.大的蜘蛛也依然是树的结构.输出大的蜘蛛的直径. 知识: 树的直径是指树上的最长简单路 求树的直径有个结论: 假设s-t这条路径为树的直径,或者称为树上的最长路. 从任意一点u出发搜到的最远的点一定是s.t中的一点,然后再从这个最远点开始搜,就可以搜到另一个最长路的端点,即用两遍广搜或者深搜就可以找出树的最长路 证明:反证法. 那回到这道题,要使得大蜘蛛的直径最大,就要使连接的小蜘蛛…

1094 - Farthest Nodes in a Tree PDF (English) Statistics Forum Time Limit: 2 second(s) Memory Limit: 32 MB Given a tree (a connected graph with no cycles), you have to find the farthest nodes in the tree. The edges of the tree are weighted and undire…

Roads in the North Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 2359   Accepted: 1157 Description Building and maintaining roads among communities in the far North is an expensive business. With this in mind, the roads are build such…

Cow Marathon Time Limit: 2000MS   Memory Limit: 30000K Total Submissions: 4185   Accepted: 2118 Case Time Limit: 1000MS Description After hearing about the epidemic of obesity in the USA, Farmer John wants his cows to get more exercise, so he has com…

题目链接:http://poj.org/problem?id=2631 题意:给出一棵树的两边结点以及权重,就这条路上的最长路. 思路:求实求树的直径. 这里给出树的直径的证明: 主要是利用了反证法: 假设 s-t这条路径为树的直径,或者称为树上的最长路 现有结论,从任意一点u出发搜到的最远的点一定是s.t中的一点,然后在从这个最远点开始搜,就可以搜到另一个最长路的端点,即用两遍广搜就可以找出树的最长路 证明:   1.设u为s-t路径上的一点,结论显然成立,否则设搜到的最远点为T则   dis…

题目链接 : https://codeforces.com/problemset/problem/961/E One day Polycarp decided to rewatch his absolute favourite episode of well-known TV series "Tufurama". He was pretty surprised when he got results only for season 7 episode 3 with his search…

对操作序列分块,每S次暴力重建主席树. 当S=sqrt(n*log(n))时,复杂度为O(m*sqrt(n*log(n))). 在线的. #include<cstdio> #include<cmath> #include<algorithm> using namespace std; #define N 500001 #define M 200001 struct Point{int x,y,z;}; bool operator < (const Point &a…

其实就是求总长度 - 一个最长“连续”自序列的长度 最长“连续”自序列即一个最长的lis,并且这个lis的值刚好是连续的,比如4,5,6... 遍历一遍,贪心就是了 遍历到第i个时,此时值为a[i],如果a[i]-1在前面已经出现过了,则len[a[i]] = len[a[i-1]]+1 否则len[a[i]] = 1 #include <cstdio> #include <algorithm> #include <cstring> #include <iostr…

Farthest Nodes in a Tree Time Limit: 2000MS Memory Limit: 32768KB 64bit IO Format: %lld & %llu Submit Status Description Given a tree (a connected graph with no cycles), you have to find the farthest nodes in the tree. The edges of the tree are weigh…

<题目链接> 题目大意: 给定一颗树,求出树的直径. 解题分析:树的直径模板题,以下程序分别用树形DP和两次BFS来求解. 树形DP: #include <cstdio> #include <algorithm> using namespace std; ; struct Edge{ int to,val,nxt; Edge(,,):to(_to),val(_val),nxt(_nxt){} }e[N<<]; int n,m,cnt,ans; int dp1…