关于宽搜的时间问题

  #define pii pair <int, int>
  #define mp make_pair
  #define x first
  #define y second
  queue <pii> q;
  q.push (mp (n + 1, m + 1));
  while (!q.empty ()) {
    pii p = q.front ();
    q.pop ();
    // Q[p.x][p.y] = 2;
    if (p.x + 1 <= n + 1 && Q[p.x + 1][p.y] == 0) {
      Q[p.x + 1][p.y] = 2; // <1>
      q.push (mp (p.x + 1, p.y));
    }
    if (p.x - 1 >= n - h + 1 && Q[p.x - 1][p.y] == 0) {
      Q[p.x - 1][p.y] = 2; // <2>
      q.push (mp (p.x - 1, p.y));
    }
    if (p.y + 1 <= m + 1 && Q[p.x][p.y + 1] == 0) {
      Q[p.x][p.y + 1] = 2; // <3>
      q.push (mp (p.x, p.y + 1));
    }
    if (p.y - 1 >= 0 && Q[p.x][p.y - 1] == 0) {
      Q[p.x][p.y - 1] = 2; // <4>
      q.push (mp (p.x, p.y - 1));
    }
  }