Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque


walk = [(1, 0), (-1, 0), (0, 1), (0, -1)]
warp = [(-2, -2), (-2, -1), (-2, 0), (-2, 1), (-2, 2),
        (-1, -2), (-1, -1), (-1, 0), (-1, 1), (-1, 2),
        (0, -2), (0, -1), (0, 1), (0, 2),
        (1, -2), (1, -1), (1, 0), (1, 1), (1, 2),
        (2, -2), (2, -1), (2, 0), (2, 1), (2, 2),]


def get_warped(walked, map_):
    warped = deque()
    while walked:
        h, w = walked.popleft()
        for i, j in warp:
            h2 = h + i
            w2 = w + j
            if -1 < h2 < H and -1 < w2 < W and map_[h2][w2] == '.':
                warped.append((h2, w2))
                map_[h2][w2] = map_[h][w] + 1
    return warped, map_


def get_walked(candidate, map_):
    walked = deque()
    while candidate:
        h, w = candidate.popleft()
        walked.append((h, w))
        for i, j in walk:
            h2 = h + i
            w2 = w + j
            if -1 < h2 < H and -1 < w2 < W and map_[h2][w2] == '.':
                candidate.append((h2, w2))
                map_[h2][w2] = map_[h][w]
    return walked, map_

H, W = map(int, input().split())
s_h, s_w = [i-1 for i in map(int, input().split())]
d_h, d_w = [i-1 for i in map(int, input().split())]
map_ = [list(input()) for i in range(H)]

candidate = deque([(s_h, s_w)])
map_[s_h][s_w] = 0

while candidate:
    walked, map_ = get_walked(candidate, map_)
    candidate, map_ = get_warped(walked, map_)

for h in range(H):
    for w in range(W):
        if map_[h][w] == '.':
            map_[h][w] = -1

print(map_[d_h][d_w])


Fixed submission:
from collections import deque
 
 
walk = [(1, 0), (-1, 0), (0, 1), (0, -1)]
warp = [(-2, -2), (-2, -1), (-2, 0), (-2, 1), (-2, 2),
        (-1, -2), (-1, -1), (-1, 0), (-1, 1), (-1, 2),
        (0, -2), (0, -1), (0, 1), (0, 2),
        (1, -2), (1, -1), (1, 0), (1, 1), (1, 2),
        (2, -2), (2, -1), (2, 0), (2, 1), (2, 2),]
 
 
def get_warped(walked, map_):
    warped = deque()
    while walked:
        h, w = walked.popleft()
        for i, j in warp:
            h2 = h + i
            w2 = w + j
            if -1 < h2 < H and -1 < w2 < W and map_[h2][w2] == '.':
                warped.append((h2, w2))
                map_[h2][w2] = map_[h][w] + 1
    return warped, map_
 
 
def get_walked(candidate, map_):
    walked = deque()
    while candidate:
        h, w = candidate.popleft()
        walked.append((h, w))
        for i, j in walk:
            h2 = h + i
            w2 = w + j
            if -1 < h2 < H and -1 < w2 < W and map_[h2][w2] == '.':
                candidate.append((h2, w2))
                map_[h2][w2] = map_[h][w]
    return walked, map_
 
H, W = map(int, input().split())
s_h, s_w = [i-1 for i in map(int, input().split())]
d_h, d_w = [i-1 for i in map(int, input().split())]
map_ = [list(input()) for i in range(H)]
 
candidate = deque([(s_h, s_w)])
map_[s_h][s_w] = 0
 
while candidate:
    walked, map_ = get_walked(candidate, map_)
    candidate, map_ = get_warped(walked, map_)
 
for h in range(H):
    for w in range(W):
        if map_[h][w] == '.':
            map_[h][w] = -1
 
print(map_[d_h][d_w])

Buggy python submission (verdict: Time Limit Exceeded):
from itertools import product


def get_magic_movable_list(movable_list, candidate_list):
    return [(h, w) for h, w in candidate_list if any((t_h, t_w) in movable_list for t_h, t_w in product([h-2, h-1, h, h+1, h+2], [w-2, w-1, w, w+1, w+2]))]


def get_movable_list(h, w, movable_list, candidate_list):
    movable_list.append((h, w))
    candidate_list.remove((h, w))
    targets = [(h+1, w), (h-1, w), (h, w+1), (h, w-1)]
    for h, w in targets:
        if (h, w) in candidate_list:
            movable_list, candidate_list = get_movable_list(h, w, movable_list, candidate_list)
    return movable_list, candidate_list

H, W = map(int, input().split())
s_h, s_w = [i-1 for i in map(int, input().split())]
d_h, d_w = [i-1 for i in map(int, input().split())]
s = [list(input()) for i in range(H)]

candidate_list = [(h, w) for h in range(H) for w in range(W) if s[h][w] == '.']
movable_list, candidate_list = get_movable_list(s_h, s_w, [], candidate_list)
i = 0

while True:
    if (d_h, d_w) in movable_list:
        break
    magic_movable_list = get_magic_movable_list(movable_list, candidate_list)

    if not magic_movable_list:
        i = -1
        break

    i += 1

    for h, w in magic_movable_list:
        if (h, w) in candidate_list:
  	        movable_list, candidate_list = get_movable_list(h, w, movable_list, candidate_list)

print(i)

Fixed submission:
from collections import deque
 
 
walk = [(1, 0), (-1, 0), (0, 1), (0, -1)]
warp = [(-2, -2), (-2, -1), (-2, 0), (-2, 1), (-2, 2),
        (-1, -2), (-1, -1), (-1, 0), (-1, 1), (-1, 2),
        (0, -2), (0, -1), (0, 1), (0, 2),
        (1, -2), (1, -1), (1, 0), (1, 1), (1, 2),
        (2, -2), (2, -1), (2, 0), (2, 1), (2, 2),]
 
 
def get_warped(walked, map_):
    warped = deque()
    while walked:
        h, w = walked.popleft()
        for i, j in warp:
            h2 = h + i
            w2 = w + j
            if -1 < h2 < H and -1 < w2 < W and map_[h2][w2] == '.':
                warped.append((h2, w2))
                map_[h2][w2] = map_[h][w] + 1
    return warped, map_
 
 
def get_walked(candidate, map_):
    walked = deque()
    while candidate:
        h, w = candidate.popleft()
        walked.append((h, w))
        for i, j in walk:
            h2 = h + i
            w2 = w + j
            if -1 < h2 < H and -1 < w2 < W and map_[h2][w2] == '.':
                candidate.append((h2, w2))
                map_[h2][w2] = map_[h][w]
    return walked, map_
 
H, W = map(int, input().split())
s_h, s_w = [i-1 for i in map(int, input().split())]
d_h, d_w = [i-1 for i in map(int, input().split())]
map_ = [list(input()) for i in range(H)]
 
candidate = deque([(s_h, s_w)])
map_[s_h][s_w] = 0
 
while candidate:
    walked, map_ = get_walked(candidate, map_)
    candidate, map_ = get_warped(walked, map_)
 
for h in range(H):
    for w in range(W):
        if map_[h][w] == '.':
            map_[h][w] = -1
 
print(map_[d_h][d_w])

Buggy python submission (verdict: Time Limit Exceeded):
from itertools import product

def add_magic_move(enable_to_move_list):
  ret = list(enable_to_move_list)
  for h, w in enable_to_move_list:
    for target_h, target_w in product([h-1, h, h+1], [w-1, w, w+1]):
      if -1 < target_h < H and -1 < target_w < W and (target_h, target_w) not in enable_to_move_list:
        s[target_h][target_w] = '.'
        ret += [(target_h, target_w)]
  return ret
    

def get_enable_to_move_list(h, w, enable_to_move_list):
  if (h, w) in enable_to_move_list:
    return enable_to_move_list
  enable_to_move_list += [(h, w)]
  targets = ((h+1, w), (h-1, w), (h, w+1), (h, w-1))
  for h, w in targets:
    if -1 < h < H and -1 < w < W and s[h][w] == '.':
      enable_to_move_list = get_enable_to_move_list(h, w, enable_to_move_list)
  return enable_to_move_list

H, W = map(int, input().split())
s_h, s_w = [i-1 for i in map(int, input().split())]
d_h, d_w = [i-1 for i in map(int, input().split())]
s = [list(input()) for i in range(H)]

enable_to_move_list = get_enable_to_move_list(s_h, s_w, [])
i = 0
while True:
  if (d_h, d_w) in enable_to_move_list:
    break
  tmp = add_magic_move(enable_to_move_list)
  i += 1
  for h, w in list(set(tmp) - set(enable_to_move_list)):
  	enable_to_move_list = get_enable_to_move_list(h, w, enable_to_move_list)
  if not set(tmp) ^ set(enable_to_move_list):
    i = -1
    break

print(i)

Fixed submission:
from collections import deque
 
 
walk = [(1, 0), (-1, 0), (0, 1), (0, -1)]
warp = [(-2, -2), (-2, -1), (-2, 0), (-2, 1), (-2, 2),
        (-1, -2), (-1, -1), (-1, 0), (-1, 1), (-1, 2),
        (0, -2), (0, -1), (0, 1), (0, 2),
        (1, -2), (1, -1), (1, 0), (1, 1), (1, 2),
        (2, -2), (2, -1), (2, 0), (2, 1), (2, 2),]
 
 
def get_warped(walked, map_):
    warped = deque()
    while walked:
        h, w = walked.popleft()
        for i, j in warp:
            h2 = h + i
            w2 = w + j
            if -1 < h2 < H and -1 < w2 < W and map_[h2][w2] == '.':
                warped.append((h2, w2))
                map_[h2][w2] = map_[h][w] + 1
    return warped, map_
 
 
def get_walked(candidate, map_):
    walked = deque()
    while candidate:
        h, w = candidate.popleft()
        walked.append((h, w))
        for i, j in walk:
            h2 = h + i
            w2 = w + j
            if -1 < h2 < H and -1 < w2 < W and map_[h2][w2] == '.':
                candidate.append((h2, w2))
                map_[h2][w2] = map_[h][w]
    return walked, map_
 
H, W = map(int, input().split())
s_h, s_w = [i-1 for i in map(int, input().split())]
d_h, d_w = [i-1 for i in map(int, input().split())]
map_ = [list(input()) for i in range(H)]
 
candidate = deque([(s_h, s_w)])
map_[s_h][s_w] = 0
 
while candidate:
    walked, map_ = get_walked(candidate, map_)
    candidate, map_ = get_warped(walked, map_)
 
for h in range(H):
    for w in range(W):
        if map_[h][w] == '.':
            map_[h][w] = -1
 
print(map_[d_h][d_w])

Buggy python submission (verdict: Time Limit Exceeded):
from itertools import product

def add_magic_move(enable_to_move_list):
  ret = list(enable_to_move_list)
  for h, w in enable_to_move_list:
    for target_h, target_w in product([h-1, h, h+1], [w-1, w, w+1]):
      if -1 < target_h < H and -1 < target_w < W and (target_h, target_w) not in enable_to_move_list:
        s[target_h][target_w] = '.'
        ret += [(target_h, target_w)]
  return ret
    

def get_enable_to_move_list(h, w, enable_to_move_list):
  if (h, w) in enable_to_move_list:
    return enable_to_move_list
  enable_to_move_list += [(h, w)]
  targets = ((h+1, w), (h-1, w), (h, w+1), (h, w-1))
  for h, w in targets:
    if -1 < h < H and -1 < w < W and s[h][w] == '.':
      enable_to_move_list = get_enable_to_move_list(h, w, enable_to_move_list)
  return enable_to_move_list

H, W = map(int, input().split())
s_h, s_w = [i-1 for i in map(int, input().split())]
d_h, d_w = [i-1 for i in map(int, input().split())]
s = [list(input()) for i in range(H)]

enable_to_move_list = get_enable_to_move_list(s_h, s_w, [])
i = 0
while True:
  if (d_h, d_w) in enable_to_move_list:
    break
  tmp = add_magic_move(enable_to_move_list)
  i += 1
  for h, w in tmp:
  	enable_to_move_list = get_enable_to_move_list(h, w, enable_to_move_list)
  if not set(tmp) ^ set(enable_to_move_list):
    i = -1
    break

print(i)

Fixed submission:
from collections import deque
 
 
walk = [(1, 0), (-1, 0), (0, 1), (0, -1)]
warp = [(-2, -2), (-2, -1), (-2, 0), (-2, 1), (-2, 2),
        (-1, -2), (-1, -1), (-1, 0), (-1, 1), (-1, 2),
        (0, -2), (0, -1), (0, 1), (0, 2),
        (1, -2), (1, -1), (1, 0), (1, 1), (1, 2),
        (2, -2), (2, -1), (2, 0), (2, 1), (2, 2),]
 
 
def get_warped(walked, map_):
    warped = deque()
    while walked:
        h, w = walked.popleft()
        for i, j in warp:
            h2 = h + i
            w2 = w + j
            if -1 < h2 < H and -1 < w2 < W and map_[h2][w2] == '.':
                warped.append((h2, w2))
                map_[h2][w2] = map_[h][w] + 1
    return warped, map_
 
 
def get_walked(candidate, map_):
    walked = deque()
    while candidate:
        h, w = candidate.popleft()
        walked.append((h, w))
        for i, j in walk:
            h2 = h + i
            w2 = w + j
            if -1 < h2 < H and -1 < w2 < W and map_[h2][w2] == '.':
                candidate.append((h2, w2))
                map_[h2][w2] = map_[h][w]
    return walked, map_
 
H, W = map(int, input().split())
s_h, s_w = [i-1 for i in map(int, input().split())]
d_h, d_w = [i-1 for i in map(int, input().split())]
map_ = [list(input()) for i in range(H)]
 
candidate = deque([(s_h, s_w)])
map_[s_h][s_w] = 0
 
while candidate:
    walked, map_ = get_walked(candidate, map_)
    candidate, map_ = get_warped(walked, map_)
 
for h in range(H):
    for w in range(W):
        if map_[h][w] == '.':
            map_[h][w] = -1
 
print(map_[d_h][d_w])