题解 | #走迷宫#

#include <queue>
using namespace std;
queue<pair<int, int> > q;
const int N = 1001;
char a[N][N];
int w[N][N];
bool b[N][N];
int x00, y00, x11, y11;
int n, m;



int dx[4] = {-1, 0, 1, 0}, dy[4] = {0, 1, 0, -1};

int bfs()
{
	memset(w, -1, sizeof(w));
	memset(b, 0, sizeof(b));
	b[x00][y00] = 1;
	q.push(make_pair(x00, y00));
	while (!q.empty())
	{
		int x1, y1;
		x1 = q.front().first, y1 = q.front().second;
		q.pop();
		for (int i = 0; i < 4; i++)
		{
			int x2 = x1 + dx[i], y2 = y1 + dy[i];
			if (x2 >= 1 && x2 <= n && y2 >= 1 && y2 <= m && b[x2][y2] == false && a[x2][y2] == '.')
			{
				b[x2][y2] = true;
				w[x2][y2] = w[x1][y1] + 1;
				q.push(make_pair(x2, y2));
			}
		}
	}
	return w[x11][y11] + 1;
}

int main()
{
	cin >> n >> m;
	cin >> x00 >> y00 >> x11 >> y11;
	for (int i = 1; i <= n; i++)
		for (int j = 1; j <= m; j++)
			cin >> a[i][j];
	if(bfs()==0)
        cout<<"-1"<<endl;
    else
        cout<<bfs();
	return 0;
}