C. Sum Balance Ujan has a lot of numbers in his boxes. He likes order and balance, so he decided to reorder the numbers. There are…

这题写起来真的有点麻烦,按照官方题解的写法 先建图,然后求强连通分量,然后判断掉不符合条件的换 最后做dp转移即可 虽然看起来复杂度很高,但是n只有15,所以问题不大 #include <iostream> #include <fstream> #include <vector> #include <set> #include <map> #include <bitset> #include <algorithm> #in…

D. 0-1 MST Ujan has a lot of useless stuff in his drawers, a considerable part of which are his math notebooks: it is time to sort them out. This time he found an old dusty graph theory notebook with a description of a graph. It is an undirected weig…

Codeforces Round #599 (Div. 2) D. 0-1 MST Description Ujan has a lot of useless stuff in his drawers, a considerable part of which are his math notebooks: it is time to sort them out. This time he found an old dusty graph theory notebook with a descr…

Hard problem 题目链接: http://codeforces.com/contest/706/problem/C Description Vasiliy is fond of solving different tasks. Today he found one he wasn't able to solve himself, so he asks you to help. Vasiliy is given n strings consisting of lowercase Engl…

题目链接:http://codeforces.com/contest/294/problem/B B. Shaass and Bookshelf time limit per test 1 second memory limit per test 256 megabytes input standard input output standard output Shaass has n books. He wants to make a bookshelf for all his books.…

D. Memory and Scores   Memory and his friend Lexa are competing to get higher score in one popular computer game. Memory starts with score a and Lexa starts with score b. In a single turn, both Memory and Lexa get some integer in the range [ - k;k] (…

题意 一棵 \(n\) 个点的树,每个点有权值 \(a_i\) .你想砍树. 你可以砍任意次,每次你选择一些边断开,需要满足砍完后每个连通块的权值和是相等的.求有多少种砍树方案. \(n \le 10^6, a_i \le 10^9\) 题解 先假设只砍一次.令所有点权和为 \(S\) ,那么假设要砍成 \(k\) 个连通块,则每个连通块的权值和均为 \(\displaystyle \frac{S}{k}\) . 考虑如何得到砍的方案,以 \(1\) 号点为根 \(dfs\) ,若当前点 \(i…

B. Obsessive String   Hamed has recently found a string t and suddenly became quite fond of it. He spent several days trying to find all occurrences of t in other strings he had. Finally he became tired and started thinking about the following proble…

D. Sum in the tree 题目链接:https://codeforces.com/contest/1099/problem/D 题意: 给出一棵树,以及每个点的si,这里的si代表从i号结点到根节点的权值和.但是有些si=-1,这就相当于丢失了当前结点的数据. 假设原本每个点的权值为ai,那么现在求sum{ai}的最小为多少,ai为非负数. 题解: 这题可以单独看每一条链上的s值,假设当前结点为u,儿子结点v,那么就有几种情况: 1.su==-1&&sv==-1,这种不用管,继…