D. Holidays Time Limit: 20 Sec Memory Limit: 256 MB 题目连接 http://codeforces.com/gym/100187/problem/D Description Everyone knows that the battle of Endor is just a myth fabled by George Lucas for promotion of his movie. Actually, no battle of Endor has
C. Kyoya and Colored Balls Time Limit: 20 Sec Memory Limit: 256 MB 题目连接 http://codeforces.com/contest/554/problem/C Description Kyoya Ootori has a bag with n colored balls that are colored with k different colors. The colors are labeled from 1 to k.
题目描述: Kyoya and Colored Balls time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output Kyoya Ootori has a bag with n colored balls that are colored with k different colors. The colors are labeled f
题目链接: http://codeforces.com/problemset/problem/272/D D. Dima and Two Sequences time limit per test2 secondsmemory limit per test256 megabytes 问题描述 Little Dima has two sequences of points with integer coordinates: sequence (a1, 1), (a2, 2), ..., (an,
C. Beautiful Numbers 题目连接: http://www.codeforces.com/contest/300/problem/C Description Vitaly is a very weird man. He's got two favorite digits a and b. Vitaly calls a positive integer good, if the decimal representation of this integer only contains
E. Mike and Geometry Problem 题目连接: http://www.codeforces.com/contest/689/problem/E Description Mike wants to prepare for IMO but he doesn't know geometry, so his teacher gave him an interesting geometry problem. Let's define f([l, r]) = r - l + 1 to
[题目]H. Ember and Storm's Tree Game [题意]Zsnuoの博客 [算法]动态规划+排列组合 [题解]题目本身其实并不难,但是大量干扰因素让题目显得很神秘. 参考:Zsnuoの博客 一.首先Ember必胜(考虑n个点连成一条链),故合法的树一定满足先手必胜.当Storm选择的链满足单调或单峰时,每一条链对答案贡献两对(i,op). 解释:单调时,考虑翻转最后一个数和从第二个数开始取负两种操作.单峰时,上凸考虑翻转顶峰和顶峰右侧的数,下凸考虑取负顶峰和顶峰右侧的数.
[题目]C. Maximum Element [题意]给定n和k,定义一个排列是好的当且仅当存在一个位置i,满足对于所有的j=[1,i-1]&&[i+1,i+k]有a[i]>a[j],求长度为n的好的排列数.n<=10^6. [算法]排列组合+动态规划 [题解]设D(n)表示长度为n且满足a[n]=n的好的排列数,考虑这样的一个排列w. 如果数字n-1的位置j<n-k,那么显然这是一个好的排列. 如果数字n-1的位置j>=n-k,那么位置j前的数字一定<n-1
Codeforces 382E Ksenia and Combinatorics Ksenia has her winter exams. Today she is learning combinatorics. Here's one of the problems she needs to learn to solve. How many distinct trees are there consisting of n vertices, each with the following pro