http://codeforces.com/contest/837/problem/D 分解质因数,即第i个数的因子2的个数为c2[i],因子5的个数为c5[i],末尾零的个数就是min{Σc2[i],Σc5[i]}. 联想到二维背包,显然因子5的个数一定时,因子2的个数越多越好,于是令f(i,j,k)为前i个数选j个且因子5的个数共有k个时最多因子2的个数,得状转方程f(i,j,k)=max{f(i-1,j-1,k-c5[i])+c2[i],f(i-1,j,k)}. 再把第一维滚掉就能过了.…

Round Corridor  Descriptions Amugae位于一个非常大的圆形走廊中.走廊由两个区域组成.内部区域等于nñ扇区,外部区域等于m米部门.在相同区域(内部或外部)的每对扇区之间存在壁,但在内部区域和外部区域之间没有壁.墙壁始终存在于12点钟位置. 内部区域的扇区被表示为(1,1),(1,2),...,(1,Ñ)(1,1),(1,2),…,(1,ñ)顺时针方向.外部区域的扇区被表示为(2,1),(2,2),...,(2,米)(2,1),(2,2),…,(2,米)以相同的方式…

[codeforces 415D]Mashmokh and ACM 题意:美丽数列定义:对于数列中的每一个i都满足:arr[i+1]%arr[i]==0 输入n,k(1<=n,k<=2000),问满足[数列长度是k && 数列中每一个元素arr[i]在1~n之间 && 数列中元素可以重复]的数列有多少个?结果对10^9+7取余 解题思路:dp[i][j]表示长度是j,最后一位是i的种数 if(kk%i==0) dp[kk][j+1]+=dp[i][j] #inc…

CF837D. Round Subset Let's call the roundness of the number the number of zeros to which it ends. You have an array of n numbers. You need to choose a subset of exactly k numbers so that the roundness of the product of the selected numbers will be ma…

time limit per test1 second memory limit per test256 megabytes inputstandard input outputstandard output Kevin Sun has just finished competing in Codeforces Round #334! The round was 120 minutes long and featured five problems with maximum point valu…

time limit per test1 second memory limit per test256 megabytes inputstandard input outputstandard output As you have noticed, there are lovely girls in Arpa's land. People in Arpa's land are numbered from 1 to n. Everyone has exactly one crush, i-th…

time limit per test3 seconds memory limit per test256 megabytes inputstandard input outputstandard output Two soldiers are playing a game. At the beginning first of them chooses a positive integer n and gives it to the second soldier. Then the second…

time limit per test2 seconds memory limit per test256 megabytes inputstandard input outputstandard output In this problem we assume the Earth to be a completely round ball and its surface a perfect sphere. The length of the equator and any meridian i…

time limit per test4 seconds memory limit per test256 megabytes inputstandard input outputstandard output Mahmoud wants to write a new dictionary that contains n words and relations between them. There are two types of relations: synonymy (i. e. the…

[题目链接]:http://codeforces.com/contest/707/problem/E [题意] 给你一个n*m的方阵; 里面有k个联通块; 这k个联通块,每个连通块里面都是灯; 给你q个操作; 有以下两种类型 ①将第i个连通块里面灯取反 ②询问你(x1,y1)(x2,y2)这个矩形区域内灯的权值的和; [题解] 要用到二维的树状数组; 取反操作只要O(1)就能完成; 即先不管它是什么,取反就是了; 然后在询问的时候,直接用二维树状数组累加; 这里的累加可能是减也可能是加; 也可能…