Codeforces Round #142 (Div. 1) C. Triangles 题目链接 今天校内选拔赛出了这个题,没做出来....自己思维能力还不够强吧.我题也给读错了.. 每次拆掉一条边,可以考虑在原图中会破坏多少三角形,但这也不好统计:所以可以转化一下,在新图中是什么样子的. 原图中会破坏三角形的话,那么在新图中,那些没有被\(a,b\)两个点连接的点的个数就应当是破坏的个数.这个好统计,就是\(n-du[a]-du[b]+\)与\(a,b\)同时相连的点的数量.这个容斥一下就出来…

A. Dragons 按\(x\)排序. B. T-primes \(x\)是平方数,且根\(\sqrt{x}\)是个质数. C. Shifts 枚举列的位置,对于每行来说,最多只会涉及4个列. D. Planets 最短路. E. Triangles 3个点可以分成4种情形:0条边,1条边,2条边,3条边. 考虑计数0和3,或1和2. 1和2至少有一条边,记与\(u\)有连边的点数为\(d_u\),则没有连边的点为\(n-1-d_u\),则\(d_u\cdot(n-1-d_u)\)构成的方案要…

B. T-primes time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output We know that prime numbers are positive integers that have exactly two distinct positive divisors. Similarly, we'll call a posit…

Problem  Codeforces Round #556 (Div. 2) - D. Three Religions Time Limit: 1000 mSec Problem Description Input Output Sample Input 51 2 1 2 1 Sample Output 1 1 1 2 2 题解:这个题有做慢了,这种题做慢了和没做出来区别不大... 读题的时候脑子里还意识到素数除了2都是奇数,读完之后就脑子里就只剩欧拉筛了,贪心地构造使得前缀和是连续的素数,那…

Codeforces Round #556 (Div. 1) A. Prefix Sum Primes 给你一堆1,2,你可以任意排序,要求你输出的数列的前缀和中质数个数最大. 发现只有\(2\)是偶质数,那么我们先放一个\(2\),再放一个\(1\),接下来把\(2\)全部放掉再把\(1\)全部放掉就行了. #include<iostream> #include<cstdio> using namespace std; inline int read() { int x=0;bo…

Codeforces Round #366 (Div. 2) A I hate that I love that I hate it水题 #I hate that I love that I hate it n = int(raw_input()) s = "" a = ["I hate that ","I love that ", "I hate it","I love it"] for i in ran…

Codeforces Round #354 (Div. 2) Problems     # Name     A Nicholas and Permutation standard input/output 1 s, 256 MB    x3384 B Pyramid of Glasses standard input/output 1 s, 256 MB    x1462 C Vasya and String standard input/output 1 s, 256 MB    x1393…

直达–>Codeforces Round #368 (Div. 2) A Brain’s Photos 给你一个NxM的矩阵,一个字母代表一种颜色,如果有”C”,”M”,”Y”三种中任意一种就输出”#Color”,如果只有”G”,”B”,”W”就输出”#Black&White”. #include <cstdio> #include <cstring> using namespace std; const int maxn = 200; const int INF =…

 cf之路,1,Codeforces Round #345 (Div. 2) ps:昨天第一次参加cf比赛,比赛之前为了熟悉下cf比赛题目的难度.所以做了round#345连试试水的深浅.....       其实这个应该是昨天就写完的,不过没时间了,就留到了今天.. 地址:http://codeforces.com/contest/651/problem/A A. Joysticks time limit per test 1 second memory limit per test 256…

Codeforces Round #279 (Div. 2) 做得我都变绿了! Problems     # Name     A Team Olympiad standard input/output 1 s, 256 MB  x2377 B Queue standard input/output 2 s, 256 MB  x1250 C Hacking Cypher standard input/output 1 s, 256 MB  x740 D Chocolate standard in…