洛谷P1466 集合 Subset Sums

#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
#include <cassert>
using namespace std;
const int MAXN = 40;

int N, M;
long long f[800];

int main()
{
    cin>>N;
    M = (N + 1) * N / 2;
    if(M & 1) {
        puts("0"); return 0;
    }
    M /= 2;
    f[0] = 1;
    for(int i = 1; i <= N; i++)
        for(int j = M; j >= i; j--)
            f[j] += f[j - i];
    cout<<f[M] / 2<<endl;
    return 0;
}