题解 for D：希望
D.pdf
我们来看看这道题的部分分：
首先明确本题的贪心策略：一旦有放置魔法符文的方案就放，这个贪心策略是显然正确的。
对于Subtask1" role="presentation" style="position: relative;">Subtask1Subtask1Subtask1：枚举树上O(N2)" role="presentation" style="position: relative;">O(N2)O(N2)O(N^2)条路径，每一条路径都O(N)" role="presentation" style="position: re
You are given a tube which is reflective inside represented as two non-coinciding, but parallel to Ox" data-mce-tabindex="0">OxOx lines. Each line has some special integer points — positions of sensors on sides of the tube. You are going to emit a laser ray in the tube. To do so, y
题目描述 给定一棵树，选择l条路径覆盖最多的点的个数是多少。 输入输出样例输入样例#1： 复制17 3
1 2
3 2
2 4
5 2
5 6
5 8
7 8
9 8
5 10
10 13
13 14
10 12
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15 17
15 16
15 10 输出样例#1： 复制13 很好的一道题，果然我的贪心技巧还不够。观察因为可以重叠，我们选叶子作为端点一定是最优的，因为如果不到叶子结点那么向叶子结点延伸一定可以覆盖更多点，因此在叶子很多的情况下我们选2*l个叶子。接下来一步就比较巧妙了，我们换一个角度，从结果来思考。最后覆盖
output standard output A tree is an undirected graph with exactly one simple path between each pair of vertices. We call a set of simple paths k" data-mce-tabindex="0">kk-valid if each vertex of the tree belongs to no more than one of these paths (including endpoints) and each path consists
题目描述A parade of all elephants is to commence soon at the Byteotian zoo. The zoo employees have encouraged these enormous animals to form a single line, as the manager wills it to be the initial figure of the parade. Unfortunately, the manager himself came to the parade and did not quite like what he
Problem StatementSnuke has a rooted tree with N vertices, numbered 1 through N. Vertex 1 is the root of the tree, and the parent of Vertex i ( 2≤i≤N ) is Vertex Pi ( Pi<i ). There is a number, 0 or 1, writte
Description聪聪研究发现，荒岛野人总是过着群居的生活，但是，并不是整个荒岛上的所有野人都属于同一个部落，野人们总是拉帮结派形成属于自己的部落，不同的部落之间则经常发生争斗。只是，这一切都成为谜团了——聪聪根本就不知道部落究竟是如何分布的。 不过好消息是，聪聪得到了一份荒岛的地图。地图上标注了N个野人居住的地点（可以看作是平面上的坐标）。我们知道，同一个部落的野人总是生活在附近。我们把两个部落的距离，定义为部落中距离最近的那两个居住点的距离。聪聪还获得了一个有意义的信息——这些野人总共被分为了K个部落！这真是个好消息。聪聪希望从这些信息里挖掘出所有部落的详细信息。他正在尝试这样一种算法
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