luoguP1441 砝码称重

#include<bits/stdc++.h>
using namespace std;
const int maxn=25;
int a[maxn],n,m,ans=0;
bool book[maxn],f[maxn*100];
void dfs(int s,int t){
    if(t==m+1){
        memset(f,0,sizeof(f));
        int len=0;
        for(int i=1;i<=n;++i)if(!book[i])len+=a[i];
        f[0]=1;
        for(int i=1;i<=n;++i){
            if(book[i])continue;
            for(int j=len;j>=a[i];--j){
                f[j]=(f[j]||f[j-a[i]]);
            }
        }
        int re=0;
        for(int i=1;i<=len;++i){
            if(f[i])++re;
        }
        ans=max(ans,re);
        return ;
    }
    if(s>n)return ;
    for(int i=s;i<=n;++i){
        book[i]=1;
        dfs(i+1,t+1);
        book[i]=0;
    }
}
int main(){
    cin>>n>>m;
    for(int i=1;i<=n;++i)cin>>a[i];
    dfs(1,1);
    cout<<ans;
    return 0;
}