1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
#include <bits/stdc++.h>

using namespace std;
using ll = long long;
const int MAXN = 3e3+5;
bool av[MAXN][MAXN];
int res = 0, n, k, p = 997, ruch[4][2] = {{1, 0}, {0, 1}, {-1, 0}, {0, -1}};
ll mod1 = 1e9+7, mod2 = 1e9+9;
unordered_set<ll> S;
void f(int lvl)
{
  ll h1 = 0, h2 = 0;
  for (int i = 1; i <= n; i++)
  {
    for (int j = 1; j <= n; j++)
    {
      int x = av[i][j] + 1;
      h1 = (h1*p + x)%mod1;
      h2 = (h2*p + x)%mod2;
    }
  }
  if (S.count(h1*h2) != 0) return;
  else if (lvl == k)
  {
    res++;
    S.insert(h1*h2);
    return;
  }
  for (int i = 1; i <= n; i++)
  {
    for (int j = 1; j <= n; j++)
    {
      if (av[i][j])
      {
        for (int l = 0; l < 4; l++)
        {
          int x = i + ruch[l][0], y = j + ruch[l][1];
          if (x == 0 || x > n || y == 0 || y > n) continue;
          if (!av[x][y])
          {
            av[i][j] = 0;
            f(lvl+1);
            av[i][j] = 1;
            break;
          }
        }
      }
    }
  }
}
int main()
{
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  cin >> n >> k;

  for (int i = 1; i <= n; i++)
  {
    for (int j = 1; j <= n; j++)
    {
      char c;
      cin >> c;
      av[i][j] = (c == '.');
    }
  }
  if (k == 1)
  {
    for (int i = 1; i <= n; i++)
    {
      for (int j = 1; j <= n; j++)
      {
        if (av[i][j])
        {
          for (int l = 0; l < 4; l++)
          {
            int x = i+ruch[l][0], y = j+ruch[l][1];
            if (x < 0 || x > n || y < 0 || y > n) continue;
            if (!av[x][y]) res++;
          }
        }
      }
    }
  }
  else f(0);

  cout << res << "\n";
}