AT2304 Cleaning 题意 一个树上每个节点有一些石子,每次只能选取两个叶子节点并将路径间的所有点上的石子数量减1,问是否能将所有石子取完. 思路 设 \(f_x\) 表示从 \(x\) 节点向上的路径条数,\(s_x\) 为子节点的 \(f\) 值的和,则有: \[a_x=\frac{s_x-f_x}{2}+f_x\\ f_x=2a_x-s_x \] 我们只需要保证以下条件即可: 从子节点传上来的路径条数的最大值小于等于该点石头个数: 向上传的路径条数不为负且小于等于该点石头数. 也…

题目链接 AtCoder:https://agc010.contest.atcoder.jp/tasks/agc010_c 洛谷:https://www.luogu.org/problemnew/show/AT2304 Solution 窝yy了好久的dpQAQ 标算很巧妙:我们考虑算每条边被经过了多少次,这里把一个叶子节点到另一个叶子节点的取石子看成\(\rm travel\). 首先选一个度数大于一的点作为根节点,然后我们分类讨论: 每个叶子节点上面的边\(cnt\)一定等于当前点的石子数.…

题目描述 Farmer John's cows, pampered since birth, have reached new heights of fastidiousness. They now require their barn to be immaculate. Farmer John, the most obliging of farmers, has no choice but hire some of the cows to clean the barn. Farmer John…

博客总目录,记录学习R与数据分析的一切:http://www.cnblogs.com/weibaar/p/4507801.html -- Sunday, January 11, 2015 课程概述 Getting and Cleaning Data是Coursera数据科学专项的第三门课,有中文翻译.但是由于中文区讨论没有英文区热闹,以及资料积累,强烈建议各位同时选报中文项目和英文项目,可以互相匹配学习. Week1的课程概括下来,主要介绍了getting and cleaning data的目…

Coursera-Getting and Cleaning Data-Week2 Saturday, January 17, 2015 课程概述 week2主要是介绍从各个来源读取数据.包括MySql,HDF5,webpage,API等,范围还蛮广. 因为工作和日常中没有直接到数据库拿数据的权限,所以暂时只是走马观花看了一遍,然后做quiz时再看一遍,留个概念即可. 下面的笔记因为主要是我自己留着以后做备查的,所以可能有些地方有点泄题.强烈建议想要好好学习,认真学习的人,优先先看一下视频,然后跟…

Coursera-Getting and Cleaning Data-Week3 Wednesday, February 04, 2015 好久不写笔记了,年底略忙.. Getting and Cleaning Data第三周其实没什么好说的,一个quiz,一个project,加一个swirl. 基本上swirl已经把第三周的内容都概括进去了.就是dplyr, tidyr以及lubridate包的学习和使用.其中dplyr专注于选择/筛选,tidyr关注于数据重塑型,二lubridate是我目前…

博客总目录:http://www.cnblogs.com/weibaar/p/4507801.html Thursday, January 29, 2015 补上第四周笔记,以及本次课程总结. 第四周课程主要针对text进行处理.里面包括 1.变量名的处理 2.正则表达式 3.日期处理(参见swirl lubridate包练习) 首先,变量名的处理,奉行两个原则,1)统一大小写tolower/toupper:2)去掉在导入数据时,因为特殊字符导致的合并变量 3)不要重复:4)少用代码缩写 使用的…

[BZOJ1672][Usaco2005 Dec]Cleaning Shifts Description Farmer John's cows, pampered since birth, have reached new heights of fastidiousness. They now require their barn to be immaculate. Farmer John, the most obliging of farmers, has no choice but hire…

http://poj.org/problem?id=2376 Cleaning Shifts Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 12604   Accepted: 3263 Description Farmer John is assigning some of his N (1 <= N <= 25,000) cows to do some cleaning chores around the barn.…

POJ 2376 Cleaning Shifts(轮班打扫) Time Limit: 1000MS   Memory Limit: 65536K [Description] [题目描述] Farmer John is assigning some of his N (1 <= N <= 25,000) cows to do some cleaning chores around the barn. He always wants to have one cow working on clean…