[C++]白俊1941号:有名な七姫

#include <bits/stdc++.h>

using namespace std;

int n[6][6], res, dir[4][2] = { {1, 0}, {-1, 0}, {0, 1}, {0, -1} };
char b[6][6];
bool visited[26];
pair<int, int> pos[26];
vector<int> v;

void func(int cnt, int idx)
{
	if (cnt == 7)
	{
		int s = 0;
		for (auto& i : v)
			if (b[pos[i].first][pos[i].second] == 'S')
				s++;

		if (s < 4)
			return;

		set<int> tmp;
		for (auto& i : v)
			tmp.insert(i);

		int num = 0;
		queue<int> q;
		q.push(v[0]);
		tmp.erase(v[0]);
		while (!q.empty())
		{
			pair<int, int> now = pos[q.front()];
			q.pop();
			num++;

			for (int i = 0; i < 4; i++)
			{
				int nr = now.first + dir[i][0], nc = now.second + dir[i][1];
				int next = n[nr][nc];

				if (nr >= 1 &&  nr <= 5 && nc >= 1 && nc <= 5 && tmp.find(next) != tmp.end())
				{
					tmp.erase(next);
					q.push(next);
				}
			}
		}

		if (num == 7)
			res++;
		return;
	}

	for (int i = idx; i <= 25; i++)
	{
		if (!visited[i])
		{
			visited[i] = true;
			v.push_back(i);
			func(cnt + 1, i + 1);
			visited[i] = false;
			v.pop_back();
		}
	}
}

int main(void)
{
	int idx = 1;
	for (int i = 1; i <= 5; i++)
		for (int j = 1; j <= 5; j++)
			cin >> b[i][j], n[i][j] = idx, pos[idx++] = { i, j };

	func(0, 1);
	cout << res;
	return 0;
}