• 2024-04-01
• BFS搜索

#include<bits/stdc++.h>


void solve()
{
	int n, m, x, y; std::cin >> n >> m >> x >> y;
	x--, y--;
	std::vector<std::string > s(n);
	for(int i = 0; i < n; i++)
	{
		std::cin >> s[i];
	}
	
	int dxy[][2] = {0, 1, 0, -1, 1, 0, -1, 0};
	int ans = 0;
	
	auto calc = [&](int x, int y)
	{
		int cnt = 0;
		for(int i = x + 1; i < n; i++)
		{
			if(s[i][y] == 'G') cnt++;
			else if(s[i][y] == '#') break;
		}
		for(int i = x - 1; i >= 0; i--)
		{
			if(s[i][y] == 'G') cnt++;
			else if(s[i][y] == '#') break;
		}
		for(int j = y + 1; j < m; j++)
		{
			if(s[x][j] == 'G') cnt++;
			else if(s[x][j] == '#') break;
		}
		for(int j = y - 1; j >= 0; j--)
		{
			if(s[x][j] == 'G') cnt++;
			else if(s[x][j] == '#') break;
		}
		return cnt;
	};
	auto BFS =[&]()
	{
		std::queue<std::pair<int,int> > q;
		std::vector<std::vector<int> > vis(n, std::vector<int>(m));
		q.push({x, y});
		while(q.size())
		{
			auto t = q.front(); q.pop();
			auto nx = t.first, ny = t.second;
			int cnt = calc(nx, ny);
			if(ans < cnt) ans = cnt;
			
			for(int i = 0; i < 4; i++)
			{
				int dx = nx + dxy[i][0];
				int dy = ny + dxy[i][1];
				
				if(dx < 0 || dx >= n || dy < 0 || dy >= m) continue;
				if(s[dx][dy] == '#' || s[dx][dy] == 'G') continue;
				
				if(vis[dx][dy]) continue;
				vis[dx][dy] = 1;
				
				q.push({dx, dy});
			}

		}
	};
	BFS();
	std::cout << ans << "\n";	
	
}
int main()
{
	std::ios::sync_with_stdio(false);
	std::cin.tie(nullptr);
	int t = 1;
	while(t--) solve();
	return 0;
}