洛谷 1441 砝码秤重

 1 #include<cstdio>
 2 #include<algorithm>
 3 #include<cstring>
 4 using namespace std;
 5 const int maxn=2010;
 6 int n,m,a[maxn],b[maxn],ans=0,tot;
 7 bool v[maxn],f[maxn];
 8 void read(int &k){
 9     k=0; int f=1; char c=getchar();
10     while(c<‘0‘||c>‘9‘)c==‘-‘&&(f=-1),c=getchar();
11     while(‘0‘<=c&&c<=‘9‘)k=k*10+c-‘0‘,c=getchar();
12     k*=f;
13 }
14 void dp(){
15     memset(f,0,sizeof(f)); tot=1; b[1]=0;
16     for (int i=1;i<=n;i++) if(v[i]){
17         int now=tot;
18         for(int j=1;j<=now;j++) if(!f[b[j]+a[i]]) f[b[j]+a[i]]=1,b[++tot]=b[j]+a[i];
19         ans=max(ans,tot-1);
20     }
21 }
22 void dfs(int dep,int tot){
23     if(dep>=n){if(tot>=n-m) dp(); return;}
24     if(tot<n-m) v[dep+1]=1,dfs(dep+1,tot+1),v[dep+1]=0;
25     dfs(dep+1,tot);
26 }
27 int main(){
28     read(n); read(m);
29     for (int i=1;i<=n;i++) read(a[i]);
30     sort(a+1,a+1+n); dfs(0,0);
31     return printf("%d\n",ans),0;
32 }