You are given a sequence of numbers a1, a2, ..., an, and a number m. Check if it is possible to choose a non-empty subsequence aij such that the sum of numbers in this subsequence is divisible by m. Input The first line contains two numbers, n and m…

http://codeforces.com/problemset/problem/577/B 题意:有n个数,求有无一个子序列满足和是m的倍数 思路:用模下的背包做,发现n是十的六次方级别,但是有个神奇的性质,就是抽屉原理,当n大于等于m的时候,总会有sum[i]和sum[j]满足sum[i]%m=sum[j]%m,于是当n>=m的时候就可以特判掉,DP的复杂度就是O(n^2)的 总结:一定要记住,在模m下的前缀和这样的东西,一定要记得有抽屉原理! 然后这题的XX细节真是坑死我了 #includ…

题目链接:http://codeforces.com/problemset/problem/448/C 题意: 给你n个数字,给定m. 问你是否能从中选出若干个数字,使得这些数字之和为m的倍数. 题解: 其实就是要找一些数字,使得之和mod m为0. 开一个vector,存当前已经能够构成的数字之和mod m之后的值. 一开始vector为空,然后枚举n个数字a[i],对于每个数字枚举当前vector中的值v[i],将没有出现过的(a[i]+v[i])%m值加入vector中. 最后判断下vec…

题目链接:http://codeforces.com/problemset/problem/577/B 题目意思:就是给出 n 个数(a1, a2, ..., an) 和 m,问能不能从这 n 个数中选出一些数(不能为空),使得这些数的总和能整除 m . 实不相瞒,完全没想法...看题解,有个地方看都看不懂: n > m的情况.求助乌冬子,连带被批英语水皮 >___<.还是谢谢他啦,一步一步引导我. 貌似挺多人也有这个疑惑的.他说那个是特例优化,原谅我懒,直接摘抄吧~ 首先要知道一些参数…

题意:给一个长度为n的正整数序列,问能不能找到一个不连续的子序列的和可以被m整除. 解法:抽屉原理+dp.首先当m<n时一定是有答案的,因为根据抽屉原理,当得到这个序列的n个前缀和%m时,一定会出现两个相同的数,这两个前缀和相减得到的序列和一定可以被m整除.当n<=m时,dp一下就可以了,类似01背包. 其实可以直接dp,只要滚动数组+在找到答案时break就可以了,同样因为抽屉原理,当枚举到第m+1个物品的时候就一定会得到解,所以最后复杂度O(m^2). 代码: #include<st…

题目链接: B. Modulo Sum time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output You are given a sequence of numbers a1, a2, ..., an, and a number m. Check if it is possible to choose a non-empty subse…

B. Modulo Sum time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output You are given a sequence of numbers a1, a2, ..., an, and a number m. Check if it is possible to choose a non-empty subsequence…

B. Modulo Sum Time Limit: 1 Sec Memory Limit: 256 MB 题目连接 http://codeforces.com/contest/577/problem/B Description You are given a sequence of numbers a1, a2, ..., an, and a number m. Check if it is possible to choose a non-empty subsequence aij such…

 Modulo Sum time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output You are given a sequence of numbers a1, a2, ..., an, and a number m. Check if it is possible to choose a non-empty subsequence a…

B. Modulo Sum time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output You are given a sequence of numbers a1, a2, ..., an, and a number m. Check if it is possible to choose a non-empty subsequence…