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BZOJ4800 [Ceoi2015]Ice Hockey World Championship

本文版权归ljh2000和博客园共有,欢迎转载,但须保留此声明,并给出原文链接,谢谢合作。

 

 

本文作者:ljh2000
作者博客:http://www.cnblogs.com/ljh2000-jump/
转载请注明出处,侵权必究,保留最终解释权!


题目链接:BZOJ4800

正解:$meet$ $in$ $the$ $middle$

解题报告:

  $meet$ $in$ $the$ $middle$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。

  

BZOJ4800 [Ceoi2015]Ice Hockey World Championship