codeforces B. Modulo Sum
2018-01-29 13:41
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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 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.
Examples
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.
题目大意:从序列里面选数字,问之和是否可以被m整除
解析:受大佬的启发,原来是一道背包题
m比较小<=1000
a[i]看成a[i]%m就可以了。
有n个0..999之间的整数。。
用那些数字凑m的倍数,也就是sum%m==0
则用cnt[0..999]记录每个数字出现的个数。
即n个物品,每个物品cnt[i]个。
然后凑和为0
多重背包。但每个物品的数量可能很多,所以加一个二进制优化.
但是照我的做法需要注意的是要多开一个dp1,作为赋值,因为01背包从后往前遍历的话,一般不会影响后面的状态,但是%是会影响的,所以判断时,用dp判断,修改dp1,最后再把dp1赋值给dp。
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 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.
Examples
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.
题目大意:从序列里面选数字,问之和是否可以被m整除
解析:受大佬的启发,原来是一道背包题
m比较小<=1000
a[i]看成a[i]%m就可以了。
有n个0..999之间的整数。。
用那些数字凑m的倍数,也就是sum%m==0
则用cnt[0..999]记录每个数字出现的个数。
即n个物品,每个物品cnt[i]个。
然后凑和为0
多重背包。但每个物品的数量可能很多,所以加一个二进制优化.
但是照我的做法需要注意的是要多开一个dp1,作为赋值,因为01背包从后往前遍历的话,一般不会影响后面的状态,但是%是会影响的,所以判断时,用dp判断,修改dp1,最后再把dp1赋值给dp。
#include <bits/stdc++.h> #define ll long long #define pb push_back #define inf 0x3f3f3f3f #define rep(i,a,b) for(int i=a;i<b;i++) #define rep1(i,a,b) for(int i=a;i>=b;i--) using namespace std; const int N=1e6+100; ll arr ; ll cnt ; int dp ; int dp1 ; int main() { ios::sync_with_stdio(false); int n,m; cin>>n>>m; memset(dp,0,sizeof dp); rep(i,0,n) { cin>>arr[i],arr[i]%=m; } rep(i,0,n) { if(arr[i]==0) {cout<<"YES"<<endl;return 0;} cnt[arr[i]]++; } dp[0]=1; rep(i,1,1000) { for(int j=1;cnt[i]!=0;j*=2) { if(j>cnt[i]) j=cnt[i]; for(int k=m-1;k>=0;k--) { if(dp[k]) { dp1[(k+j*i)%m]=1; //cout<<i<<' '<<j<<' '<<k<<' '<<(k+j*i)%m<<endl; if((k+j*i)%m==0) { cout<<"YES"<<endl; return 0; } } } for(int k=m-1;k>=0;k--) if(dp1[k]) dp[k]=1; cnt[i]-=j; } } cout<<"NO"<<endl; return 0; }
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