【JZOJ5264】化学

#include <cstdio>
#include <iostream>
#include <algorithm>
#include <cstring>
#include <cmath>
#include <iostream>
#define ll long long
using namespace std;
ll coss[50],f[1<<22];
ll n,m,tot,nn,anss=0;

void dfs1(int now,int co){
    if(co>m) return;
    if(now==nn+1){
        f[++tot]=co;
        return;
    }
    dfs1(now+1,co+coss[now]);
    dfs1(now+1,co);
}

void dfs2(int now,int co){
    if(co>m) return;
    if(now==n+1){
        int l=1,r=tot,mid,ans=0;
        while(l<=r){
            mid=(l+r)/2;
            if(f[mid]+co<=m) ans=mid,l=mid+1;
            else r=mid-1;
        }
        anss+=ans;
        return;
    }
    dfs2(now+1,co+coss[now]);
    dfs2(now+1,co);
}

int main()
{
    scanf("%lld%lld",&n,&m);nn=n/2;
    for(int i=1;i<=n;i++) scanf("%lld",&coss[i]);
    dfs1(1,0);
    sort(f+1,f+tot+1);
    dfs2(nn+1,0);
    printf("%lld",anss);
    return 0;
}