SPOJ ASSIGN

#define ll long long
#include <bits/stdc++.h>
using namespace std;

const int OO = 1e9;
const double EPS = 1e-9;

ll mem[(1 << 20)];
int n;

vector<vector<int>> k;

ll solve(bitset<20> msk) {
    int idx = msk.count();
    if(idx == n) {
        return 1;
    }
    if(mem[msk.to_ullong()] != -1) {
        return mem[msk.to_ullong()];
    }
    ll &ret = mem[msk.to_ullong()];
    ret = 0;
    for(int e : k[idx]) {
        if(!msk[e]) {
            bitset<20> cp = msk;
            cp[e] = 1;
            ret += solve(cp);
        }
    }
    return ret;
}

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);
    int t;
    cin >> t;
    while(t--) {
        cin >> n;
        k.clear();
        k.resize(n);
        for(int i = 0; i < n; i++) {
            for(int j = 0; j < n; j++) {
                bool b;
                cin >> b;
                if(b) {
                    k[i].push_back(j);
                }
            }
        }
        for(int i = (1 << n)-1; i >= 0; i--) {
            mem[i] = -1;
        }
        bitset<20> msk;
        cout << solve(msk) << "\n";
    }
    return 0;
}