技巧(9)子数列和整除
Modulo Sum
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 (1 ≤ n ≤ 106, 2 ≤ m ≤ 103) — the size of the original sequence and the number such that sum should be divisible by it.
The second line contains n integers a1, a2, ..., an (0 ≤ ai ≤ 109).
Output
In the single line print either "YES" (without the quotes) if there exists the sought subsequence, or "NO" (without the quotes), if such subsequence doesn't exist.
input
3 5
1 2 3
output
YES
input
1 6
5
output
NO
input
4 6
3 1 1 3
output
YES
input
6 6
5 5 5 5 5 5
output
YES
Note
In the first sample test you can choose numbers 2 and 3, the sum of which is divisible by 5.
In the second sample test the single non-empty subsequence of numbers is a single number 5. Number 5 is not divisible by 6, that is, the sought subsequence doesn't exist.
In the third sample test you need to choose two numbers 3 on the ends.
In the fourth sample test you can take the whole subsequence.
#include<cstdio>
#include<algorithm>
#include<cstring> const int maxn = 1e6+5; using namespace std; int a[maxn]; bool vis[1005]; vector<int>myvec; int main(){ myvec.push_back(0); int n,m; scanf("%d%d",&n,&m); for(int i = 0; i < n; i++){ scanf("%d",&a[i]); } for(int i = 0; i < n; i++){ int siz = myvec.size(); for(int j = 0; j < siz; j++){ if((a[i]+myvec[j])%m==0){puts("YES");return 0;} if(!vis[(a[i]+myvec[j])%m]){ vis[(a[i]+myvec[j])%m] = 1; myvec.push_back((a[i]+myvec[j])%m); } } } puts("NO"); return 0; }

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