algospot - picnic

//algospot - picnic
 
#include <iostream>
#include <vector>
using namespace std;
 
int N, M;
vector<vector<int>> duo;
vector<bool> sold;
int ans;
int check;
 
void init()
{
    check = ans = 0;
    cin >> N >> M;
    duo = vector<vector<int>>(N);
    sold = vector<bool>(N, false);
    int x, y;
    for(int i = 0; i<M; i++)
    {
        cin >> x >> y;
        duo[x].push_back(y);
        duo[y].push_back(x);
    }
}
 
void bf(int idx)
{
    if(idx == N)
    {
        if(check == N/2)
            ++ans;
        return;
    }
    else if(sold[idx])
    {
        bf(idx+1);
        return;
    }
 
    for(int i = 0; i<duo[idx].size(); ++i)
    {
        if(!sold[duo[idx][i]])
        {
            sold[idx] = sold[duo[idx][i]] = true;
            ++check;
            bf(idx+1);
            --check;
            sold[idx] = sold[duo[idx][i]] = false;
        }
    }
}
 
int main()
{
    int C; cin >> C;
    for(int t_num = 0; t_num < C; ++t_num)
    {
        init();
        bf(0);
        cout << ans << "\n";
    }
}