CF785D Anton and School - 2 题意:给定一个长度\(\le 2 \times 10e5\)由'('和')'组成的字符串,问有多少个子串(可以不连续),前半部分是由\('('\)组成后半部分由\(')'\)组成. 考虑枚举每一个可能的字串的中间,然后统计两边 先预处理每一个位置前面有多少个\('('\),后面有多少个\(')'\) 然后枚举每一个\('('\)表示中间且必选 设当前位(包括)有\(a\)个\('('\) 则对此位置的答案即为\(\sum_{i=0}^{mi…

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题目链接 problem 给出一个括号序列,要求删除一些括号使得剩下的括号序列是个匹配的括号序列,且改括号序列左边全部为左括号,右边全部为右括号. solution 考虑枚举左右括号交界的位置\(x\),为了避免重复计算,强制要求\(x\)左边的第一个左括号必选.然后枚举\(x\)的时候只枚举左括号的位置. 然后枚举括号序列的长度.假设长度为\(2i\),那么左右括号就分别有\(i\)个,假设左边有\(n\)个左括号,右边有\(m\)个右括号.那么该位置的答案就是\(\sum\limits_{i…

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…