Codeforces 932.D Tree

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D. Tree time limit per test 2 seconds memory limit per test 512 megabytes input standard input output standard output You are given a node of the tree with index 1 and with weight 0. Let cnt be the number of nodes in the tree at any instant (initiall…

Problem - D - Codeforces Fix a Tree

Problem - D - Codeforces Fix a Tree 看完第一名的代码,顿然醒悟... 我可以把所有单独的点全部当成线,那么只有线和环. 如果全是线的话,直接线的条数-1,便是操作数. 如果有环和线,环被打开的同时,接入到线上.那就是线和环的总数-1. 如果只有环的话,把所有的环打开,互相接入,共需n次操作. #include <cstdio> #include <algorithm> using namespace std; ; int cur[maxn];…

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Codeforces 932 E. Team Work（组合数学）

http://codeforces.com/contest/932/problem/E 题意: 可以看做有n种小球,每种小球有无限个,先从中选出x种,再在这x种小球中任选k个小球的方案数选出的x种不一样,任选k个球的顺序不一样均视做不同的方案 f[i][j] 表示选了i个小球,来自j种的方案数那么答案就是考虑选的第i个球是否是选过的一种, f[i][j]=f[i-1][j]*j+f[i-1][j-1]*(n-(j-1)) #include<cstdio> #include<…

codeforces 570 D. Tree Requests 树状数组+dfs搜索序

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【19.77%】【codeforces 570D】Tree Requests

time limit per test2 seconds memory limit per test256 megabytes inputstandard input outputstandard output Roman planted a tree consisting of n vertices. Each vertex contains a lowercase English letter. Vertex 1 is the root of the tree, each of the n …