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


H, W = map(int, input().split())
CH, CW = map(int, input().split())
DH, DW = map(int, input().split())
S = ['#' * (W+4)] * 2
for i in range(H):
    S.append('##' + input() + '##')
S.append('#' * (W+4))
S.append('#' * (W+4))

CH += 2
CW += 2
DH += 2
DW += 2

dist = [[-1 for i in range(W + 4)] for j in range(H + 4)]
dist[CH - 1][CW - 1] = 0
q = deque()
q.append([CH, CW])

while len(q) != 0:
    current_pos = q.popleft()
    y = current_pos[0]
    x = current_pos[1]
    if (y, x) == (DH, DW):
        print(dist[DH - 1][DW - 1])
        exit()

    for i in range(-2, 3):
        for j in range(-2, 3):
            if i == j == 0:
                continue
            next_y = y + i
            next_x = x + j

            if S[next_y - 1][next_x - 1] == '#':
                continue
            if dist[next_y - 1][next_x - 1] == dist[y - 1][x - 1]:
                continue

            if dist[next_y - 1][next_x - 1] == -1 or dist[next_y - 1][next_x - 1] > dist[y - 1][x - 1]:
                if (i == 0 and j in (-1, 1)) or (j == 0 and i in (-1, 1)):
                    q.appendleft([next_y, next_x])
                    dist[next_y - 1][next_x - 1] = dist[y - 1][x - 1]
                else:
                    if dist[next_y - 1][next_x - 1] == -1:
                        q.append([next_y, next_x])
                        dist[next_y - 1][next_x - 1] = dist[y - 1][x - 1] + 1

print(-1)


Fixed submission:
from collections import deque


H, W = map(int, input().split())
CH, CW = map(int, input().split())
DH, DW = map(int, input().split())
S = ['#' * (W+4)] * 2
for i in range(H):
    S.append('##' + input() + '##')
S.append('#' * (W+4))
S.append('#' * (W+4))

CH += 2
CW += 2
DH += 2
DW += 2

dist = [[-1 for i in range(W + 4)] for j in range(H + 4)]
dist[CH - 1][CW - 1] = 0
q = deque()
q.append([CH, CW])

while len(q) != 0:
    current_pos = q.popleft()
    y = current_pos[0]
    x = current_pos[1]
    if (y, x) == (DH, DW):
        print(dist[DH - 1][DW - 1])
        exit()

    for i in range(-2, 3):
        for j in range(-2, 3):
            if i == j == 0:
                continue
            next_y = y + i
            next_x = x + j

            if S[next_y - 1][next_x - 1] == '#':
                continue
            if dist[next_y - 1][next_x - 1] == dist[y - 1][x - 1]:
                continue

            if dist[next_y - 1][next_x - 1] == -1 or dist[next_y - 1][next_x - 1] > dist[y - 1][x - 1]:
                if (i == 0 and j in (-1, 1)) or (j == 0 and i in (-1, 1)):
                    q.appendleft([next_y, next_x])
                    dist[next_y - 1][next_x - 1] = dist[y - 1][x - 1]
                else:
                    if dist[next_y - 1][next_x - 1] == -1:
                        q.append([next_y, next_x])
                        dist[next_y - 1][next_x - 1] = dist[y - 1][x - 1] + 1

print(-1)

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


H, W = map(int, input().split())
CH, CW = map(int, input().split())
DH, DW = map(int, input().split())
S = ['#' * (W+4)] * 2
for i in range(H):
    S.append('##' + input() + '##')
S.append('#' * (W+4))
S.append('#' * (W+4))

CH += 2
CW += 2
DH += 2
DW += 2

dist = [[-1 for i in range(W + 4)] for j in range(H + 4)]
dist[CH - 1][CW - 1] = 0
q = deque()
q.append([CH, CW])

while len(q) != 0:
    current_pos = q.popleft()
    y = current_pos[0]
    x = current_pos[1]
    for i in range(-2, 3):
        for j in range(-2, 3):
            if i == j == 0:
                continue
            next_y = y + i
            next_x = x + j

            if S[next_y - 1][next_x - 1] == '#':
                continue
            if dist[next_y - 1][next_x - 1] == dist[y - 1][x - 1]:
                continue

            if dist[next_y - 1][next_x - 1] == -1 or dist[next_y - 1][next_x - 1] > dist[y - 1][x - 1]:
                q.append([next_y, next_x])
                if (i == 0 and j in (-1, 1)) or (j == 0 and i in (-1, 1)):
                    dist[next_y - 1][next_x - 1] = dist[y - 1][x - 1]
                else:
                    if dist[next_y - 1][next_x - 1] == -1:
                        dist[next_y - 1][next_x - 1] = dist[y - 1][x - 1] + 1

print(dist[DH - 1][DW - 1])


Fixed submission:
from collections import deque


H, W = map(int, input().split())
CH, CW = map(int, input().split())
DH, DW = map(int, input().split())
S = ['#' * (W+4)] * 2
for i in range(H):
    S.append('##' + input() + '##')
S.append('#' * (W+4))
S.append('#' * (W+4))

CH += 2
CW += 2
DH += 2
DW += 2

dist = [[-1 for i in range(W + 4)] for j in range(H + 4)]
dist[CH - 1][CW - 1] = 0
q = deque()
q.append([CH, CW])

while len(q) != 0:
    current_pos = q.popleft()
    y = current_pos[0]
    x = current_pos[1]
    if (y, x) == (DH, DW):
        print(dist[DH - 1][DW - 1])
        exit()

    for i in range(-2, 3):
        for j in range(-2, 3):
            if i == j == 0:
                continue
            next_y = y + i
            next_x = x + j

            if S[next_y - 1][next_x - 1] == '#':
                continue
            if dist[next_y - 1][next_x - 1] == dist[y - 1][x - 1]:
                continue

            if dist[next_y - 1][next_x - 1] == -1 or dist[next_y - 1][next_x - 1] > dist[y - 1][x - 1]:
                if (i == 0 and j in (-1, 1)) or (j == 0 and i in (-1, 1)):
                    q.appendleft([next_y, next_x])
                    dist[next_y - 1][next_x - 1] = dist[y - 1][x - 1]
                else:
                    if dist[next_y - 1][next_x - 1] == -1:
                        q.append([next_y, next_x])
                        dist[next_y - 1][next_x - 1] = dist[y - 1][x - 1] + 1

print(-1)

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


H, W = map(int, input().split())
CH, CW = map(int, input().split())
DH, DW = map(int, input().split())
S = ['#' * (W+4)] * 2
for i in range(H):
    S.append('##' + input() + '##')
S.append('#' * (W+4))
S.append('#' * (W+4))

CH += 2
CW += 2
DH += 2
DW += 2

dist = [[-1 for i in range(W + 4)] for j in range(H + 4)]
dist[CH - 1][CW - 1] = 0
q = deque()
q.append([CH, CW])

while len(q) != 0:
    current_pos = q.popleft()
    y = current_pos[0]
    x = current_pos[1]
    for i in range(-2, 3):
        for j in range(-2, 3):
            if i == j == 0:
                continue
            next_y = y + i
            next_x = x + j

            if S[next_y - 1][next_x - 1] == '#':
                continue
            if dist[next_y - 1][next_x - 1] == dist[y - 1][x - 1]:
                continue

            if dist[next_y - 1][next_x - 1] == -1 or dist[next_y - 1][next_x - 1] > dist[y - 1][x - 1]:
                q.append([next_y, next_x])
                if (i == 0 and j in (-1, 1)) or (j == 0 and i in (-1, 1)):
                    dist[next_y - 1][next_x - 1] = dist[y - 1][x - 1]
                else:
                    if dist[next_y - 1][next_x - 1] == -1:
                        dist[next_y - 1][next_x - 1] = dist[y - 1][x - 1] + 1

print(dist[DH - 1][DW - 1])


Fixed submission:
from collections import deque


H, W = map(int, input().split())
CH, CW = map(int, input().split())
DH, DW = map(int, input().split())
S = ['#' * (W+4)] * 2
for i in range(H):
    S.append('##' + input() + '##')
S.append('#' * (W+4))
S.append('#' * (W+4))

CH += 2
CW += 2
DH += 2
DW += 2

dist = [[-1 for i in range(W + 4)] for j in range(H + 4)]
dist[CH - 1][CW - 1] = 0
q = deque()
q.append([CH, CW])

while len(q) != 0:
    current_pos = q.popleft()
    y = current_pos[0]
    x = current_pos[1]
    if (y, x) == (DH, DW):
        print(dist[DH - 1][DW - 1])
        exit()

    for i in range(-2, 3):
        for j in range(-2, 3):
            if i == j == 0:
                continue
            next_y = y + i
            next_x = x + j

            if S[next_y - 1][next_x - 1] == '#':
                continue
            if dist[next_y - 1][next_x - 1] == dist[y - 1][x - 1]:
                continue

            if dist[next_y - 1][next_x - 1] == -1 or dist[next_y - 1][next_x - 1] > dist[y - 1][x - 1]:
                if (i == 0 and j in (-1, 1)) or (j == 0 and i in (-1, 1)):
                    q.appendleft([next_y, next_x])
                    dist[next_y - 1][next_x - 1] = dist[y - 1][x - 1]
                else:
                    if dist[next_y - 1][next_x - 1] == -1:
                        q.append([next_y, next_x])
                        dist[next_y - 1][next_x - 1] = dist[y - 1][x - 1] + 1

print(-1)