BZOJ 4800 Ice Hockey World Championship

折半。用一边的去查另一边。

不知不觉500了啊。。。

#include<iostream>
#include<cstdio>
#include<cstdio>
#include<algorithm>
#define maxs 1500050
#define maxn 45
using namespace std;
long long n,m,p[maxn],tab[2][maxs],ans=0,n1;
void dfs(long long now,long long top,long long ret,long long type)
{
    if (now==top)
    {
        tab[type][++tab[type][0]]=ret;
        return;
    }
    dfs(now+1,top,ret+p[now],type);
    dfs(now+1,top,ret,type);
}
int main()
{
    scanf("%lld%lld",&n,&m);
    for (long long i=1;i<=n;i++) scanf("%lld",&p[i]);
    if (n<=1) {printf("%lld\n",(p[1]<=m)+1LL);return 0;}
    n1=n>>1;
    dfs(1,n1+1,0,0);dfs(n1+1,n+1,0,1);
    sort(tab[0]+1,tab[0]+tab[0][0]+1);
    sort(tab[1]+1,tab[1]+tab[1][0]+1);
    for (long long i=1;i<=tab[0][0];i++)
    {
        long long l=1,r=tab[1][0],ret=0;
        while (l<=r)
        {
            long long mid=(l+r)>>1;
            if (tab[1][mid]<=m-tab[0][i]) {ret=mid;l=mid+1;}
            else r=mid-1;
        }
        ans+=ret;
    }
    printf("%lld\n",ans);
    return 0;
}