题目: (我的题目很长,你忍一下--) 题目分析: 这道题目的体面比较复杂,先是讲了一下树是怎样的一个结构,并且告诉我们在这里,他是以什么样的一种方式描述一棵树的,就是通过描述每个节点的父节点是哪个(b数组),然后告诉我们要安排边权,使得树中的每个节点到根的距离都能如同p数组那样进行排序,然后叫我们输出对应每个点和他的父结点之间的边权即可. 题解: 首先这道题是一道非常经典的让我们判断能否构造一个数组,使得题干条件成立,如果不能输出-1: 既然这样的话,我们肯定要先分析什么情况下会输出-1,那么…

题目链接:Weights on Vertices and Edges 题目大意:有一个\(n\)个点\(m\)条边的无向图,点有点权,边有边权,问至少删去多少条边使得对于剩下的每一条边,它所在的联通块的点权值和大于等于该边的边权 其实是蛮简单的一道题目,为什么当时就自闭了呢... 正向删边明显不靠谱,于是我们考虑反向加边,答案就是\(m-\)加入的边数 我们按照边权排序,使用并查集维护点权值和,同时记录一个\(cnt\)数组表示当前存在于该联通块内但未加入答案的边数 如果说当前联通块的点权值和大…

题目链接:https://atcoder.jp/contests/nikkei2019-qual/tasks/nikkei2019_qual_e 题意:给出一个 n 个点 m 条边的无向图,每个点和每条边都有权值,让你删除一些边,使得最终的图中满足条件:一条边存在当且仅当包含该边的连通块的点权值和大于等于该边权值,问最少要移走多少条边. 题解:删边不好做,考虑加边,对于每条边,判断加入是否合法.按边权从小到大排序进行加边,要加入一条边之前,若之前两点不连通,则合并起来变成一个连通块,可以用并查集…

定义两点的距离$d(x,y)$为$x$到$y$路径上边权异或和,则两棵树相同当且仅当$\forall 1\le i\le n$,$d(1,i)$相同 新建一个节点0,连边$(0,1)$,初始权值为0,且不能以这条边为对象操作(但操作与1相连的边会影响其) 记$d_{i}=d(0,i)$,考虑一次操作$(x,y)$对$d_{i}$的影响,恰好是交换$d_{x}$和$d_{y}$ 最终,令$a_{i}$为目标树中$d(1,i)$的值,即要求$d_{i}\oplus d_{1}=a_{i}$ 同时,记…

1663: Tree Time Limit: 5 Sec  Memory Limit: 128 MB Submit: 26  Solved: 11 [Submit][id=1663">Status][pid=1663">Web Board] Description CSU has a lot of trees. But there is a tree which is different from the others. This one is made of weight…

Description Xenia the programmer has a tree consisting of n nodes. We will consider the tree nodes indexed from 1 to n. We will also consider the first node to be initially painted red, and the other nodes — to be painted blue. The distance between t…

Alyona and the Tree 题目链接: http://acm.hust.edu.cn/vjudge/contest/121333#problem/C Description Alyona decided to go on a diet and went to the forest to get some apples. There she unexpectedly found a magic rooted tree with root in the vertex 1, every v…

  http://codeforces.com/contest/348/problem/B   B. Apple Tree time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output You are given a rooted tree with n vertices. In each leaf vertex there's a sin…

C. Alyona and the Tree 题目连接: http://www.codeforces.com/contest/682/problem/C Description Alyona decided to go on a diet and went to the forest to get some apples. There she unexpectedly found a magic rooted tree with root in the vertex 1, every verte…

C. Alyona and the Tree time limit per test 1 second memory limit per test 256 megabytes input standard input output standard output Alyona decided to go on a diet and went to the forest to get some apples. There she unexpectedly found a magic rooted…