题目描述 Bessie is planning the annual Great Cow Gathering for cows all across the country and, of course, she would like to choose the most convenient location for the gathering to take place. Bessie正在计划一年一度的奶牛大集会,来自全国各地的奶牛将来参加这一次集会.当然,她会选择最方便的地点来举办这次集会…

传送门 解题思路 首先第一遍dfs预处理出每个点的子树的siz,然后可以处理出放在根节点的答案,然后递推可得其他答案,递推方程 sum[u]=sum[x]-(val[i]*siz[u])+(siz[1]-siz[u])*val[i] 代码 #include<iostream> #include<cstdio> #include<cstring> #include<cstdlib> #include<cmath> using namespace s…

题目描述 Bessie is planning the annual Great Cow Gathering for cows all across the country and, of course, she would like to choose the most convenient location for the gathering to take place. Each cow lives in one of N (1 <= N <= 100,000) different ba…

题目描述 Bessie is planning the annual Great Cow Gathering for cows all across the country and, of course, she would like to choose the most convenient location for the gathering to take place. Bessie正在计划一年一度的奶牛大集会,来自全国各地的奶牛将来参加这一次集会.当然,她会选择最方便的地点来举办这次集会…

题目大意:给你一棵树,每个点有点权,边有边权,求一个点,使得其他所有点到这个点的距离和最短,输出这个距离 题解:树形$DP$,思路清晰,转移显然 卡点:无 C++ Code: #include <cstdio> #include <algorithm> #define maxn 100010 const long long inf = 0x3f3f3f3f3f3f3f3f; int head[maxn], cnt; struct Edge { int to, nxt, w; } e…

题目传送门 首先这道题是在树上进行的,然后求最小的不方便程度,比较符合dp的性质,那么我们就可以搞一搞树形dp. 设计状态:f[i]表示以i作为聚集地的最小不方便程度.那么我们还需要各点间的距离,但是由于本题数据加强到1e5,开二维数组显然是不现实的,我们可以换一种思路,求d[i]表示其他所有奶牛到 i点的距离和,这样就成功转化过来惹==. d[u]+=d[v]+size[v]*edge[i].val 然后再预处理size[i]数组表示以i为根的子树上奶牛的数量.这些都是一遍dfs就能搞定的,然…

题目描述 Bessie is planning the annual Great Cow Gathering for cows all across the country and, of course, she would like to choose the most convenient location for the gathering to take place. Bessie正在计划一年一度的奶牛大集会,来自全国各地的奶牛将来参加这一次集会.当然,她会选择最方便的地点来举办这次集会…

题目链接 Solution 辣鸡题...因为一个函数名看了我贼久. 思路很简单,可以先随便指定一个根,然后考虑换根的变化. 每一次把根从 \(x\) 换成 \(x\) 的一个子节点 \(y\),记录一下每个节点的子树牛数目 \(son\). 令 \(sum\) 为所有节点上牛的数目,那么每一次换根变化为 \((sum-son_y*2)*w\). 然后就可以统计了,复杂度 \(O(n)\) . Code #include<bits/stdc++.h> #define N 100008 #defi…

题目描述 Bessie is planning the annual Great Cow Gathering for cows all across the country and, of course, she would like to choose the most convenient location for the gathering to take place. Bessie正在计划一年一度的奶牛大集会,来自全国各地的奶牛将来参加这一次集会.当然,她会选择最方便的地点来举办这次集会…

题目描述 Bessie is planning the annual Great Cow Gathering for cows all across the country and, of course, she would like to choose the most convenient location for the gathering to take place. Bessie正在计划一年一度的奶牛大集会,来自全国各地的奶牛将来参加这一次集会.当然,她会选择最方便的地点来举办这次集会…