public int bfs(pair <int, int> p1, pair <int, int> p2, pair <int, int> p3)
{
int N = p3.ff;
int M = p3.ss;
Queue <pair <pair <int, int>, int> > Que;
Dictionary <pair <int, int>, bool> Vis;
Que.Enqueue(mpa(p1, 0));
while (Que.Count != 0)
{
pair <pair <int, int>, int> temp = Que.front();
Que.pop();
if (temp.ff.ff == p2.ff && temp.ff.ss == p2.ss)
{
return(temp.ss);
}
int x = temp.ff.ff;
int y = temp.ff.ss;
int dis = temp.ss + 1;
if (Vis.count(mpa(x, y)))
{
continue;
}
Vis[mpa(x, y)] = true;
for (int i = 0; i < 8; ++i)
{
int x1 = x + dx[i];
int y1 = y + dy[i];
if (valid(x1, y1, N, M))
{
Que.push(mpa(mpa(x1, y1), dis));
}
}
}
return(-1);
}