题解 | #神奇的口袋#

#include<iostream>
#include<algorithm>
using namespace std;
int cnt = 0;
void dfs(int v[],int n,int total,int pos){
    if(total == 40){
        cnt++;
        return;
    }
    else
        for(int i = pos;i < n;++i)
           dfs(v,n,total + v[i],i + 1);
}
int main()
{
    int n;
    cin >> n;
    int *v = new int[n];
    for(int i = 0;i < n;++i)
        cin >> v[i];
    sort(v,v + n);
    dfs(v,n,0,0);
    cout << cnt;
}