题意翻译 给你一棵树,每次挑选这棵树的两个叶子,加上他们之间的边数(距离),然后将其中一个点去掉,问你边数(距离)之和最大可以是多少. 题目描述 You are given an unweighted tree with n n n vertices. Then n−1 n-1 n−1 following operations are applied to the tree. A single operation consists of the following steps: choose t…

D. Roman Digits time limit per test 1 second memory limit per test 256 megabytes input standard input output standard output Let's introduce a number system which is based on a roman digits. There are digits I, V, X, L which correspond to the numbers…

<题目链接> 题目大意: 现在有无限个 1,5,10,50这四个数字,从中恰好挑选n个数字,问你这些数字的和总共有多少种不同的情况. 解题分析: 由于此题 n 的范围特别大,达到了1e9,所以猜想可能会有什么规律,使得答案在极短的时间内求解出来,于是就对本题前100项进行暴力打表,发现从第11项之后,每一项都与前一项相差49,然后本题就可以A了. /*#include <cstdio> //暴力打表找出前100项的规律 #include <map> #include &…

题意: 我们在研究罗马数字.罗马数字只有4个字符,I,V,X,L分别代表1,5,10,100.一个罗马数字的值为该数字包含的字符代表数字的和,而与字符的顺序无关.例如XXXV=35,IXI=12． 现在求问一个长度为 nnn 的罗马数字可以有多少种不同的值. n<=109n<=10^9n<=109. 题解: 我们可以用暴力的方法求出前20项的值,其中前111111 项采用打表的方式,而从第12项开始答案始终 = 前一项的答案 + 49,即 292+(n−11)∗49292+(n-11)*…

C - Convert to Ones 给你一个01串 x是反转任意子串的代价 y是将子串全部取相反的代价 问全部变成1的最小代价 两种可能 一种把1全部放到一边 然后把剩下的0变成1  要么把所有的 0 直接变成1 #include<bits/stdc++.h> using namespace std; #define LL long long int main(){ LL n,x,y; string a; cin>>n>>x>>y>>a; ;…

目录 Codeforces 998 A.Balloons B.Cutting C.Convert to Ones D.Roman Digits E.Sky Full of Stars(容斥 计数) Codeforces 998 比赛链接 A.Balloons 输出啥看错WA\(*2\)+第一次写sort写了cmp()但是没加cmpWA\(*2\)(结构体重载运算符后遗症).. 没谁了. #include <cstdio> #include <cctype> #include <…

D. Roman and Numbers time limit per test 4 seconds memory limit per test 512 megabytes input standard input output standard output Roman is a young mathematician, very famous in Uzhland. Unfortunately, Sereja doesn't think so. To make Sereja change h…

Roman and Numbers time limit per test 4 seconds memory limit per test 512 megabytes input standard input output standard output Roman is a young mathematician, very famous in Uzhland. Unfortunately, Sereja doesn't think so. To make Sereja change his…

Roman numerals are represented by seven different symbols: I, V, X, L, C, D and M. Symbol Value I 1 V 5 X 10 L 50 C 100 D 500 M 1000 For example, two is written as II in Roman numeral, just two one's added together. Twelve is written as, XII, which i…

题目链接: http://codeforces.com/problemset/problem/401/D D. Roman and Numbers time limit per test4 secondsmemory limit per test512 megabytes 问题描述 Roman is a young mathematician, very famous in Uzhland. Unfortunately, Sereja doesn't think so. To make Sere…