CSP模拟赛#4 权值(T2-26)

Posted 2020-11-30 zbsy-wwx

题目地址

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 基本思想：

• 初始状态（[0]）.
• 小范围表示大范围.

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#include<cstdio>
#include<iostream>
#include<algorithm>
#define int long long
using namespace std;
const int MAXN=8000,INF=2e9,MOD=1e9+7;
int a[MAXN],f[MAXN][MAXN],p[MAXN];
signed main(){
	int n;
	cin>>n;
	p[0]=1;
	for(int i=1;i<=n;i++){
		p[i]=p[i-1]*2;
		p[i]%=MOD;
	}
	int maxx=-INF;
	for(int i=1;i<=n;i++){
		scanf("%d",&a[i]);
		maxx=max(a[i],maxx);
	}
	sort(a+1,a+n+1);
	int ans=0;
	f[0][0]=1;
	for(int i=1;i<=n;i++){
		for(int j=0;j<=maxx;j++){
			f[i][j]+=f[i-1][j];
			f[i][j]=f[i][j]%MOD;
			if(a[i]<=j+1){
				if(a[i]+j<=maxx){
					f[i][j+a[i]]+=f[i-1][j];
					f[i][j+a[i]]=f[i][j+a[i]]%MOD;
				}
				else {
					ans+=p[n-i]*f[i-1][j];
					ans=ans%MOD;
				}
			}
		}
	}
	for(int i=1;i<=maxx;i++){
		ans+=f[n][i];
		ans%=MOD;
	}
	cout<<ans<<endl;
	return 0;
}