题目大意 给你两棵树,结点分别是1-A与1-B,然后给了N台设备,并且A树和B树的叶子结点(两棵树的叶子节点数量相同)都是链接电机的.问,最多可以删掉几条边使得每个设备都能连到任意一棵(或两棵)树的根节点(1号点) 思路 对于每棵树,维护\(val[cnt][i][j]\),\(cnt\)是那个树表示我删掉这个子树的所有边之后,\([i,j]\)这个范围的设备不保证能够全部连上我的根. 用一个\(f[i]\)表示\([1,i]\)区间内,全都能连上根最多能删除多少条边,那么转移就是\(f[i]=…

F. Economic Difficulties 题目链接: https://codeforces.com/contest/1263/problem/F 题目大意: 两棵树,都有n个叶子节点,一棵树正着放,一棵树倒着放,叶子节点从左到右对应装置1,2,3,4...n,问最多能删掉多少条边,使得装置能与两棵树任意一个根节点1相连. 解题思路: mp[ i ][ j ]是装置 i 到 j 这段区间删除这段连续区间所能删除的最大边数,两个图分开看,算出每一个图中如果不连通这段区间对应的叶子节点所能删除…

F. Economic Difficulties An electrical grid in Berland palaces consists of 2 grids: main and reserve. Wires in palaces are made of expensive material, so selling some of them would be a good idea! Each grid (main and reserve) has a head node (its num…

Educational Codeforces Round 40 F. Runner's Problem 题意: 给一个$ 3 * m \(的矩阵,问从\)(2,1)$ 出发 走到 \((2,m)\) 的方案数 \(mod 1e9 + 7\), 走的规则和限制如下: From the cell (i, j) you may advance to: (i - 1, j + 1) - only if i > 1, (i, j + 1), or (i + 1, j + 1) - only if i <…

传送门 感觉脑子还是转得太慢了QAQ,一些问题老是想得很慢... A. Sweet Problem 签到. Code /* * Author: heyuhhh * Created Time: 2019/11/29 22:36:19 */ #include <iostream> #include <algorithm> #include <vector> #include <cmath> #include <set> #include <ma…

A. Sweet Problem (找规律) 题目链接 大致思路: 有一点瞎猜的,首先排一个序, \(a_1>a_2>a_3\) ,发现如果 \(a_1>=a_2+a_3\) ,那么答案肯定是 \(a_2+a_3\) ,然后发现发现规律当 \(a_2==a_3\) 的时候,还可以贡献 \((a_1+a_2+a_3)/2\) 的答案,所以只要 \(a_1\) 和 \(a_2\) 减掉一个值就可以了. B. PIN Codes (暴力) 题目链接 大致思路: 可以知道,存在一个数字不同的pi…

Codeforces Round #603 (Div. 2) A. Sweet Problem A. Sweet Problem time limit per test 1 second memory limit per test 256 megabytes input standard input output standard output You have three piles of candies: red, green and blue candies: the first pile…

题目:Economic Difficulties 传送门:https://codeforces.com/contest/1263/problem/F 题意:给了两棵tree:Ta(拥有a个节点,节点编号为[n+1, n+a]) Tb(拥有b个节点, 节点编号: [n+ a + 1, n + a + b]) 其中两颗tree的叶子节点按照dfs序依次连续连向 $ i, i \in [1, n] $节点,询问最多可以去掉多少的tree上节点,使得每一个$i , i \in [1, n]$ 仍然可以连…

E. Editor The development of a text editor is a hard problem. You need to implement an extra module for brackets coloring in text. Your editor consists of a line with infinite length and cursor, which points to the current character. Please note that…

链接: https://codeforces.com/contest/1263/problem/E 题意: The development of a text editor is a hard problem. You need to implement an extra module for brackets coloring in text. Your editor consists of a line with infinite length and cursor, which point…