折半查找

#include<map>
#include<stdio.h>
#include<iostream>
using namespace std;

long long box[50];
long long pos[50];
int main()
{
    long long n, m;
    cin >> n >> m;

    for (long long i = 0; i < n; i++)
    {
        cin >> box[i];
    }

    long long cnt = n / 2;
    map<long long, long long>a;
    for (long long i = 0; i < (1ll << cnt); i++)
    {
        long long ans = 0;
        for (long long j = 0; j < cnt; j++)
        {
            if (i & (1ll << j))
            {
                ans += box[j];
            }
        }
        a[ans] = i;
    }

    cnt = n - cnt;
    for (long long i = 0; i < (1ll << cnt); i++)
    {
        long long ans = 0;
        for (long long j = 0; j < cnt; j++)
        {
            if (i & (1ll << j))
            {
                ans += box[n - cnt + j];
                pos[j] = 1;
            }
            else
                pos[j] = 0;
        }

        if (a[m - ans])
        {
            for (long long j = 0; j < cnt; j++)
            {
                if (a[m-ans] & (1ll << j))
                {
                    cout << "1";
                }
                else
                {
                  cout << "0";
                }
            }
            break;
        }
    }
     
    for (long long i = 0; i < cnt; i++)
    {
        cout << pos[i];
    }
    return 0;
}