# BZOJ4800 [Ceoi2015]Ice Hockey World Championship

$meet$ $in$ $the$ $middle$一眼题==

$40$就分成两半，分别做完之后，那一半到另一半去查找就好了。

//It is made by ljh2000
//有志者，事竟成，破釜沉舟，百二秦关终属楚；苦心人，天不负，卧薪尝胆，三千越甲可吞吴。
#include <algorithm>
#include <iostream>
#include <cstdlib>
#include <cstring>
#include <complex>
#include <vector>
#include <cstdio>
#include <string>
#include <bitset>
#include <queue>
#include <cmath>
#include <ctime>
#include <map>
#include <set>
#define lc root<<1
#define rc root<<1|1
#define pr pair<int,int>
#define MP make_pair
#define fr first
#define sc second
#define rep(i,j,k) for(int i=j;i<=k;++i)
#define per(i,j,k) for(int i=j;i>=k;--i)
#define reg(i,x) for(int i=first[x];i;i=next[i])
using namespace std;
typedef long long LL;
typedef long double LB;
typedef complex<double> C;
const double pi = acos(-1);
const double eps = 1e-9;
const int MAXN = 2000011;
int n,lim,cnt,l,r;
LL m,ans,c[MAXN],a[45];

inline LL getint(){
LL w=0,q=0; char c=getchar(); while((c<'0'||c>'9') && c!='-') c=getchar();
if(c=='-') q=1,c=getchar(); while (c>='0'&&c<='9') w=w*10+c-'0',c=getchar(); return q?-w:w;
}

inline void dfs(int x,LL sum){
if(sum>m) return ;
if(x==lim+1) { c[++cnt]=sum; return ; }
dfs(x+1,sum+a[x]); dfs(x+1,sum);
}

inline void dfs2(int x,LL sum){
if(sum>m) return ;
if(x==lim+1) {
if(c[1]+sum>m) return ;
l=1; r=cnt; int mid,pos=0;
while(l<=r) {
mid=(l+r)>>1;
if(sum+c[mid]<=m) pos=mid,l=mid+1;
else r=mid-1;
}
ans+=pos;
return ;
}
dfs2(x+1,sum+a[x]);
dfs2(x+1,sum);
}

inline void work(){
n=getint(); m=getint();
rep(i,1,n) a[i]=getint();
int mid=n>>1;
lim=mid; dfs(1,0);
sort(c+1,c+cnt+1);
lim=n; dfs2(mid+1,0);
printf("%lld",ans);
}

int main()
{
#ifndef ONLINE_JUDGE
freopen("4800.in","r",stdin);
freopen("4800.out","w",stdout);
#endif
work();
return 0;
}
//有志者，事竟成，破釜沉舟，百二秦关终属楚；苦心人，天不负，卧薪尝胆，三千越甲可吞吴。


posted @ 2017-04-01 19:51  ljh_2000  阅读(526)  评论(0编辑  收藏  举报