纯GCC版:

#include <stdio.h>
int t, n, sx, sy, ex, ey, xx, yy, dx[] = {0, 0, 1, -1}, dy[] = {1, -1, 0, 0};
char a[100][100];
short flag;
short check(int x, int y)
{
	return x >= 0 && x < n && y >= 0 && y < n && a[x][y] == '.';
}
void dfs(int sx, int sy)
{
	if(sx == ex && sy == ey)
	{
		flag = 1;
		return;
	}
	a[sx][sy] = '#';
	for(int i = 0; i < 4; i ++)
	{
		xx = sx + dx[i];
		yy = sy + dy[i];
		if(check(xx, yy))
			dfs(xx, yy);
	}
	return;
}
int main()
{
	scanf("%d\n", &t);
	while(t --)
	{
		scanf("%d\n", &n);
		for(int i = 0; i < n; i ++)
			scanf("%s", &a[i]);
		scanf("%d %d %d %d\n", &sx, &sy, &ex, &ey);
		dfs(sx, sy);
		puts(flag ? "YES" : "NO");
		flag = 0;
	}
	return 0;
}