题目大意:给你一棵树,每个点有点权a_{i},求$\sum _{i=1}^{n} \sum _{j=i}^{n} f(i,j)$,$f(i,j)$表示i,j,路径上的点的最大权值-最小权值 正解的思路好神啊 正解: 首先,原式可以拆成$\sum _{i=1}^{n} \sum _{j=i}^{n} max(i,j) \; - \; \sum _{i=1}^{n} \sum _{j=i}^{n} min(i,j)$ max的求法和min类似,这里只讨论min的求法 把点按照从大到小排序,依次加入树…

[题目]F. Imbalance Value of a Tree [题意]给定n个点的带点权树,求所有路径极差的和.n,ai<=10^6 [算法]并查集 [题解]先计算最大值的和,按点权从小到大排序,每个点x和相邻的已访问点的点集形成的路径的最大值都是a[x],因为已访问过的点点权较小,然后用并查集并起来.复杂度O(n log n). #include<cstdio> #include<algorithm> using namespace std; ; ]; int n,a[…

[CF915F]Imbalance Value of a Tree 题目大意: 一棵\(n(n\le10^6)\)个结点的树,每个结点有一个权值\(w_i\).定义\(I(i,j)\)为\(i\)到\(j\)之间简单路径上最大权值与最小权值之差,求\(\displaystyle\sum_{i=1}^n\sum_{j=1}^nI(i,j)\). 思路: 分别计算路径最大权值之和与最小权值之和.以最大权值之和为例,在图中按权值从大到小枚举每一个点,则对于该连通块中每一个经过该点的路径,该点为路径上权…

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…

Is It A Tree? Time Limit:1000MS     Memory Limit:10000KB     64bit IO Format:%I64d & %I64u Submit Status 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 direct…