详解见：http://bonniebbs.is-programmer.com/posts/40073.html

#include <iostream>
#include <cstring>
#define N 10005
using namespace std;

int abs(int n)
{
    if(n<0) return -n;
    else return n;
}
int main()
{
    string str;
    int c1[N], c2[N], ans[N];
    int n, a, s, cnt;
    while(cin>>n)
    {
        memset(c1, 0, sizeof(c1));
        memset(c2, 0, sizeof(c2));
        memset(ans, 0, sizeof(ans));
        s = cnt = 0;
        cin >> a;
        c1[0] = 1;
        c1[a] = 1;
        s += a;
        for(int i=0; i<n-1; i++)
        {
            cin >> a;
            for(int j=0; j<=s; j++)
            {
                if(c1[j])
                {
                    c2[j+a] += c1[j];
                    c2[j] += c1[j];
                }
            }
            for(int j=1; j<=s; j++)
            {
                if(c1[j])
                {
                    c2[abs(j-a)] += c1[j];
                }
            }
            s += a;
            for(int j=0; j<=s; j++)
            {
                c1[j] = c2[j];
                c2[j] = 0;
            }
        }
        for(int i=0; i<=s; i++)
        {
            if(c1[i]==0) 
            {
                cnt++;
                ans[cnt] = i;
            }
        }
        cout << cnt << endl;
        if(cnt) 
        {
            for(int i=1; i<cnt; i++)
                cout << ans[i] << " ";
            cout << ans[cnt] << endl;
        }
    }
    return 0;
}