ACDream 1726 A Math game (折半查找)

#include<cstdio>
#include<iostream>
#include<cstring>
#include<cmath>
#include<stdlib.h>
#include<vector>
#include<queue>
#include<stack>
#include<algorithm>
#define LL long long
using namespace std;
const int MAXN=2e6+7;
int n,H;
int a[MAXN],sum[MAXN];
int main()
{
    int n,H;
    while(scanf("%d %d",&n,&H)!=EOF)
    {
        for(int i=0;i<n;i++)
            scanf("%d",&a[i]);
        int c=0,k=n>>1;
        for(int i=0;i<(1<<k);i++)
        {
            LL s=0;
            for(int j=0;j<k;j++)
            {
                if((1<<j)&i) s+= a[j];
            }
            if(s<=H) sum[c++]=s;
        }
        sort(sum,sum+c);
        int res=n-k;
        bool ok=false;
        for (int i=0;i<(1<<res);i++)
        {
            LL s=0;
            for(int j=0;j<res;j++)
            {
                if ((1<<j)&i) s+=a[k+j];
            }
            if (s>H) continue;
            if (sum[lower_bound(sum,sum+c,H-s)-sum]==H-s) {
                ok=true;
                break;
            }
        }
        puts(ok?"Yes":"No");
    }
    return 0;
}