Cutting Tree 题目连接: https://icpcarchive.ecs.baylor.edu/index.php?option=com_onlinejudge&Itemid=8&page=show_problem&problem=4922 Description Tree in graph theory refers to any connected graph (of nodes and edges) which has no simple cycle, while…

https://icpcarchive.ecs.baylor.edu/index.php?option=com_onlinejudge&Itemid=8&page=show_problem&problem=4922 题意是给定一颗森林,然后每次都可以删除一条边,或者询问某两个点是否连通. 如果顺着做是不行的.因为并查集路径压缩了,是删不了边的,(据说不路径压缩能AC,) 所以考虑逆向操作.首先不能把已经删除了的边加进去森林里面,先处理出最终状态,然后倒着模拟,就能把删边操作等价于变…

[题目]:(地址:) http://acm.hust.edu.cn/vjudge/contest/view.action?cid=97671#problem/E [题意]: 给出多棵树和两类操作:操作(C  x)删除结点 x 与其父结点的连边:操作(Q a b)询问 a b 是否连通. [解题思路]: 连通性的查询容易想到用并查集,关键在于如何处理删边. 考虑到删边的难点在于查询时的路径压缩导致某些结点与其父结点"不直接相连",这里使用离线处理,在查询之前把所有该删的边删除,同时逆序处…

总体来说,这个题给的时间比较长,样例也是比较弱的,别的方法也能做出来. 我第一次使用的是不合并路径的并查集,几乎是一种暴力,花了600多MS,感觉还是不太好的,发现AC的人很多都在300MS之内的过得. 看到他们的做法后,我知道了这个题比较好的做法. 逆向思维的并查集,因为这里只有去边操作,完全可以离线计算,把删边当成加边,然后逆序输出答案即可. 但是,这个却有一个坑,很坑,只有第一次删除的时候,我们才对他进行操作,加边的时候也只能在第一次删除的时候加.当时因为这里,十分困惑-- 这是我无路径压…

Is It A Tree? Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others) Total Submission(s): 16702    Accepted Submission(s): 3761 Problem Description A tree is a well-known data structure that is either empty (null, void, n…

Is It A Tree? Time Limit: 1000MS   Memory Limit: 10000K Total Submissions: 26002   Accepted: 8879 Description A tree is a well-known data structure that is either empty (null, void, nothing) or is a set of one or more nodes connected by directed edge…

Petya loves lucky numbers. We all know that lucky numbers are the positive integers whose decimal representations contain only the lucky digits 4 and 7. For example, numbers 47, 744, 4 are lucky and 5, 17, 467 are not. One day Petya encountered a tre…

tree 把每条边权是1的边断开,发现每个点离他最近的点个数就是他所在的连通块大小. 开一个并查集,每次读到边权是0的边就合并.最后Ans​i​​=size[findset(i)],size表示每个并查集根的size Ans_i=size[findset(i)],sizeAns​i​​=size[findset(i)],size表示每个并查集根的sizesize. #include<cstdio> #include<cstring> #include<algorithm>…

题目链接:http://acm.swust.edu.cn/problem/856/ Time limit(ms): 1000 Memory limit(kb): 10000 Description There are N trees in a forest. At first, each tree contains only one node as its root. And each node is marked with a number. You're asked to do the fo…

D. Fix a Tree time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output A tree is an undirected connected graph without cycles. Let's consider a rooted undirected tree with n vertices, numbered 1 th…