func_code_string: #include <bits/stdc++.h>   using namespace std;   double dp[1 << 20][20], p[20][20];   bool mark[1 << 20][20];   int n;   double mem(int mask, int winner) {     if (!mask) return (winner == 1);     if (mark[mask][winner]) return dp[mask][winner];     mark[mask][winner] = true;     double &ret = dp[mask][winner];     for (int i = 1; i < n; i++)       if (mask & (1 << i)) {         double tmp = 0;         tmp += p[i][winner] * mem(mask ^ (1 << i), i);         tmp += p[winner][i] * mem(mask ^ (1 << i), winner);         ret = max(ret, tmp);       }     return ret;   }   int main() {     ios_base::sync_with_stdio(0);     cin >> n;     for (int i = 1; i <= n; i++) {       p[i][0] = 1;       for (int j = 1; j <= n; j++) cin >> p[i][j];     }     n++;     cout << setprecision(10) << fixed << mem((1 << n) - 2, 0) << endl;     return 0;   }   