传送门 题意 给出一个只包含'(',')'的字符序列,询问有多少个\(RSBS\) 分析 首先需要知道一个公式 \[\sum_{i=0}^{min(x,y)}C_x^i*C_y^i=C_{x+y}^x\] 接下来我们观察第i个'(',假设它左边有x个'(',右边有y个')',那么包含它的RSBS有多少个?答案是\(C_{x+y-1}^x\),因为它已经"消耗了"一个')',所以左边的'('只能与右边的y-1个')'匹配.最后扫一遍即可. 代码 #include<bits/stdc…

赛前任务 tags:任务清单 前言 现在xzy太弱了,而且他最近越来越弱了,天天被爆踩,天天被爆踩 题单不会在作业部落发布,所以可(yi)能(ding)会不及时更新 省选前的练习莫名其妙地成为了Noip前的杂题训练,我也很无奈啊 做完了的扔最后,欢迎好题推荐 这么多题肯定是完不成了,能多做一道是一道吧 DP yyb真是强得不要不要的辣:http://www.cnblogs.com/cjyyb/category/1036536.html [ ] [SDOI2010]地精部落 https://www…

E. Anton and Tree time limit per test: 3 seconds memory limit per test :256 megabytes input:standard input output: standard output Anton is growing a tree in his garden. In case you forgot, the tree is a connected acyclic undirected graph. There are …

题目传送门 /* 题意:从前面找一个数字和末尾数字调换使得变成偶数且为最大 贪心:考虑两种情况:1. 有偶数且比末尾数字大(flag标记):2. 有偶数但都比末尾数字小(x位置标记) 仿照别人写的,再看自己的代码发现有清晰的思维是多重要 */ #include <cstdio> #include <iostream> #include <algorithm> #include <cmath> #include <cstring> #include…

E. Anton and Tree 题目连接: http://codeforces.com/contest/734/problem/E Description Anton is growing a tree in his garden. In case you forgot, the tree is a connected acyclic undirected graph. There are n vertices in the tree, each of them is painted bla…

D. Anton and Chess 题目连接: http://codeforces.com/contest/734/problem/D Description Anton likes to play chess. Also, he likes to do programming. That is why he decided to write the program that plays chess. However, he finds the game on 8 to 8 board to…

C. Anton and Making Potions 题目连接: http://codeforces.com/contest/734/problem/C Description Anton is playing a very interesting computer game, but now he is stuck at one of the levels. To pass to the next level he has to prepare n potions. Anton has a…

B. Anton and Digits 题目连接: http://codeforces.com/contest/734/problem/B Description Recently Anton found a box with digits in his room. There are k2 digits 2, k3 digits 3, k5 digits 5 and k6 digits 6. Anton's favorite integers are 32 and 256. He decide…

A. Anton and Danik 题目连接: http://codeforces.com/contest/734/problem/A Description Anton likes to play chess, and so does his friend Danik. Once they have played n games in a row. For each game it's known who was the winner - Anton or Danik. None of th…

题目链接: http://codeforces.com/contest/734/problem/D D. Anton and Chess time limit per test4 secondsmemory limit per test256 megabytes 问题描述 Anton likes to play chess. Also, he likes to do programming. That is why he decided to write the program that pla…