「POJ 1741」Tree

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题面: Tree Give a tree with n vertices,each edge has a length(positive integer less than 1001). Define dist(u,v)=The min distance between node u and v. Give an integer k,for every pair (u,v) of vertices is called valid if and only if dist(u,v) not exce…

「POJ 3666」Making the Grade 题解（两种做法）

0前言感谢yxy童鞋的dp及暴力做法! 1 算法标签优先队列.dp动态规划+滚动数组优化 2 题目难度提高/提高+ CF rating:2300 3 题面「POJ 3666」Making the Grade 路面修整 4 分析题面 4.1 简要描述给出数列 \(A\), 求非严格单调不上升或单调不下降, 且\(S=\sum^N_{i=1}|A_i-B_i|\) 最小的序列\(B\),输出\(S\) 4.2 模型转换输入\(N\), 然后输入\(N\)个数,求最小的改动这些数使之成非严…

【POJ 1741】 Tree (树的点分治)

Tree Description Give a tree with n vertices,each edge has a length(positive integer less than 1001). Define dist(u,v)=The min distance between node u and v. Give an integer k,for every pair (u,v) of vertices is called valid if and only if dist(u,v…

【POJ 1741】Tree

Tree Time Limit: 1000MS Memory Limit: 30000K Total Submissions: 11570 Accepted: 3626 Description Give a tree with n vertices,each edge has a length(positive integer less than 1001). Define dist(u,v)=The min distance between node u and v. Give a…

【POJ 1741】 Tree

[题目链接] http://poj.org/problem?id=1741 [算法] 点分治要求距离不超过k的点对个数,不妨将路径分成两类 : 1. 经过根节点 2. 不经过根节点考虑第1类路径,不妨从根节点进行一次深度优先遍历,求出每个点与根节点的距离,将距离排序,然后用两个指针扫描一遍即可,注意要减掉多算的然后,递归地计算子节点的第一类路径,即可但是这样是会超时的,我们不妨每次选择子树的重心进行计算这样做法的时间复杂度存在上界 : O(Nlog^2N) [代码] #include…

「POJ Challenge」生日礼物

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「POJ 3268」Silver Cow Party

更好的阅读体验 Portal Portal1: POJ Portal2: Luogu Description One cow from each of N farms \((1 \le N \le 1000)\) conveniently numbered \(1 \cdots N\) is going to attend the big cow party to be held at farm #X \((1 \le X \le N)\). A total of \(M (1 \le M \l…