Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque
"""
01-BFS
"""

h, w = map(int, input().split())
ch, cw = map(int, input().split())
dh, dw = map(int, input().split())
ch-=1; cw-=1; dh-=1; dw-=1
area = [list(input()) for _ in range(h)]
inf = 10**100
dist = [[inf]*w for i in range(h)]
dwalk = [(0, 1), (0, -1), (1, 0), (-1, 0)]

q = deque([(ch, cw)])
dist[ch][cw] = 0
while q:
    y, x = q.popleft()
    for dy, dx in dwalk:
        py = y+dy; px = x+dx
        if not 0<=py<h: continue
        if not 0<=px<w: continue
        if area[py][px]=='#': continue
        if dist[py][px]>dist[y][x]:
            dist[py][px] = dist[y][x]
            q.appendleft((py, px))
    for dy in range(-2, 3):
        for dx in range(-2, 3):
            py = y+dy; px = x+dx
            if not 0<=py<h: continue
            if not 0<=px<w: continue
            if area[py][px]=='#': continue
            if dist[py][px]>dist[y][x]+1:
                dist[py][px] = dist[y][x]+1
                q.append((py, px))

if dist[dh][dw] == inf:
    print(-1)
else:
    print(dist[dh][dw])

Fixed submission:
from collections import deque
import sys
input = sys.stdin.readline
h, w = map(int, input().split())
ch, cw = map(int, input().split())
dh, dw = map(int, input().split())
ch-=1; cw-=1; dh-=1; dw-=1
area = [list(input()) for _ in range(h)]
inf = 10**100
dist = [[inf]*w for i in range(h)]

dwalk = [(0, 1), (0, -1), (1, 0), (-1, 0)]

def Dijkstra(ch, cw):
    import heapq
    edgelist = [(0, ch, cw)]
    heapq.heapify(edgelist)
    dist[ch][cw] = 0
    while len(edgelist):
        cost, y, x = heapq.heappop(edgelist)
        if y==dh and x==dw:
            return dist
        if dist[y][x] < cost: continue
        for next_y, next_x in dwalk:
            if 0<=y+next_y<h and 0<=x+next_x<w:
                if area[y+next_y][x+next_x]=='#': continue
                if dist[y+next_y][x+next_x]>cost:
                    dist[y+next_y][x+next_x] = cost
                    heapq.heappush(edgelist, (cost, y+next_y, x+next_x))
        for next_y in range(-2, 3):
            for next_x in range(-2, 3):
                    if 0<=y+next_y<h and 0<=x+next_x<w:
                        if area[y+next_y][x+next_x]=='#': continue
                        if dist[y+next_y][x+next_x]>cost+1:
                            dist[y+next_y][x+next_x] = cost+1
                            heapq.heappush(edgelist, (cost+1, y+next_y, x+next_x))
    return dist

dist = Dijkstra(ch, cw)
if dist[dh][dw] == inf:
    print(-1)
else:
    print(dist[dh][dw])

Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque
import sys
input = sys.stdin.readline

"""
ダイクストラ　ギリギリ
"""
h, w = map(int, input().split())
ch, cw = map(int, input().split())
dh, dw = map(int, input().split())
ch-=1; cw-=1; dh-=1; dw-=1
area = [list(input()) for _ in range(h)]
inf = 10**100
dist = [[inf]*w for i in range(h)]

dwalk = [(0, 1), (0, -1), (1, 0), (-1, 0)]

def Dijkstra(ch, cw):
    import heapq
    edgelist = [(0, ch, cw)]
    heapq.heapify(edgelist)
    dist[ch][cw] = 0
    while len(edgelist):
        cost, y, x = heapq.heappop(edgelist)
        if y==dh and x==dw:
            return dist
        # この枝刈がないと通らない
        if dist[y][x] < cost: continue
        for next_y, next_x in dwalk:
            if 0<=y+next_y<h and 0<=x+next_x<w:
                if area[y+next_y][x+next_x]=='#': continue
                if dist[y+next_y][x+next_x]>cost:
                    dist[y+next_y][x+next_x] = cost
                    heapq.heappush(edgelist, (cost, y+next_y, x+next_x))
        for next_y in range(-2, 3):
            for next_x in range(-2, 3):
                    if 0<=y+next_y<h and 0<=x+next_x<w:
                        if area[y+next_y][x+next_x]=='#': continue
                        if dist[y+next_y][x+next_x]>cost+1:
                            dist[y+next_y][x+next_x] = cost+1
                            heapq.heappush(edgelist, (cost+1, y+next_y, x+next_x))
    return dist

dist = Dijkstra(ch, cw)
if dist[dh][dw] == inf:
    print(-1)
else:
    print(dist[dh][dw])

Fixed submission:
from collections import deque
import sys
input = sys.stdin.readline
h, w = map(int, input().split())
ch, cw = map(int, input().split())
dh, dw = map(int, input().split())
ch-=1; cw-=1; dh-=1; dw-=1
area = [list(input()) for _ in range(h)]
inf = 10**100
dist = [[inf]*w for i in range(h)]

dwalk = [(0, 1), (0, -1), (1, 0), (-1, 0)]

def Dijkstra(ch, cw):
    import heapq
    edgelist = [(0, ch, cw)]
    heapq.heapify(edgelist)
    dist[ch][cw] = 0
    while len(edgelist):
        cost, y, x = heapq.heappop(edgelist)
        if y==dh and x==dw:
            return dist
        if dist[y][x] < cost: continue
        for next_y, next_x in dwalk:
            if 0<=y+next_y<h and 0<=x+next_x<w:
                if area[y+next_y][x+next_x]=='#': continue
                if dist[y+next_y][x+next_x]>cost:
                    dist[y+next_y][x+next_x] = cost
                    heapq.heappush(edgelist, (cost, y+next_y, x+next_x))
        for next_y in range(-2, 3):
            for next_x in range(-2, 3):
                    if 0<=y+next_y<h and 0<=x+next_x<w:
                        if area[y+next_y][x+next_x]=='#': continue
                        if dist[y+next_y][x+next_x]>cost+1:
                            dist[y+next_y][x+next_x] = cost+1
                            heapq.heappush(edgelist, (cost+1, y+next_y, x+next_x))
    return dist

dist = Dijkstra(ch, cw)
if dist[dh][dw] == inf:
    print(-1)
else:
    print(dist[dh][dw])

Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque
import sys
input = sys.stdin.readline
h, w = map(int, input().split())
ch, cw = map(int, input().split())
dh, dw = map(int, input().split())
ch-=1; cw-=1; dh-=1; dw-=1
area = [list(input()) for _ in range(h)]
inf = 10**100
dist = [[inf]*w for i in range(h)]

dwalk = [(0, 1), (0, -1), (1, 0), (-1, 0)]

def Dijkstra(ch, cw):
    import heapq
    edgelist = [(0, ch, cw)]
    heapq.heapify(edgelist)
    dist[ch][cw] = 0
    while len(edgelist):
        cost, y, x = heapq.heappop(edgelist)
        if y==dh and x==dw:
            return dist
        for next_y, next_x in dwalk:
            if 0<=y+next_y<h and 0<=x+next_x<w:
                if area[y+next_y][x+next_x]=='#': continue
                if dist[y+next_y][x+next_x]>cost:
                    dist[y+next_y][x+next_x] = cost
                    heapq.heappush(edgelist, (cost, y+next_y, x+next_x))
        for next_y in range(-2, 3):
            for next_x in range(-2, 3):
                    if 0<=y+next_y<h and 0<=x+next_x<w:
                        if area[y+next_y][x+next_x]=='#': continue
                        if dist[y+next_y][x+next_x]>cost+1:
                            dist[y+next_y][x+next_x] = cost+1
                            heapq.heappush(edgelist, (cost+1, y+next_y, x+next_x))
    return dist

dist = Dijkstra(ch, cw)
if dist[dh][dw] == inf:
    print(-1)
else:
    print(dist[dh][dw])

Fixed submission:
from collections import deque
import sys
input = sys.stdin.readline
h, w = map(int, input().split())
ch, cw = map(int, input().split())
dh, dw = map(int, input().split())
ch-=1; cw-=1; dh-=1; dw-=1
area = [list(input()) for _ in range(h)]
inf = 10**100
dist = [[inf]*w for i in range(h)]

dwalk = [(0, 1), (0, -1), (1, 0), (-1, 0)]

def Dijkstra(ch, cw):
    import heapq
    edgelist = [(0, ch, cw)]
    heapq.heapify(edgelist)
    dist[ch][cw] = 0
    while len(edgelist):
        cost, y, x = heapq.heappop(edgelist)
        if y==dh and x==dw:
            return dist
        if dist[y][x] < cost: continue
        for next_y, next_x in dwalk:
            if 0<=y+next_y<h and 0<=x+next_x<w:
                if area[y+next_y][x+next_x]=='#': continue
                if dist[y+next_y][x+next_x]>cost:
                    dist[y+next_y][x+next_x] = cost
                    heapq.heappush(edgelist, (cost, y+next_y, x+next_x))
        for next_y in range(-2, 3):
            for next_x in range(-2, 3):
                    if 0<=y+next_y<h and 0<=x+next_x<w:
                        if area[y+next_y][x+next_x]=='#': continue
                        if dist[y+next_y][x+next_x]>cost+1:
                            dist[y+next_y][x+next_x] = cost+1
                            heapq.heappush(edgelist, (cost+1, y+next_y, x+next_x))
    return dist

dist = Dijkstra(ch, cw)
if dist[dh][dw] == inf:
    print(-1)
else:
    print(dist[dh][dw])

Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque
import sys
input = sys.stdin.readline
h, w = map(int, input().split())
ch, cw = map(int, input().split())
dh, dw = map(int, input().split())
ch-=1; cw-=1; dh-=1; dw-=1
area = [list(input()) for _ in range(h)]
inf = 10**100
dist = [[inf]*w for i in range(h)]

dwalk = [(0, 1), (0, -1), (1, 0), (-1, 0)]

def Dijkstra(ch, cw):
    import heapq
    edgelist = [(0, ch, cw)]
    heapq.heapify(edgelist)
    dist[ch][cw] = 0
    while len(edgelist):
        cost, y, x = heapq.heappop(edgelist)
        dist[y][x] = cost
        if y==dh and x==dw:
            return dist
        for next_y, next_x in dwalk:
            if 0<=y+next_y<h and 0<=x+next_x<w:
                if area[y+next_y][x+next_x]=='#': continue
                if dist[y+next_y][x+next_x]>cost:
                    dist[y+next_y][x+next_x] = cost
                    heapq.heappush(edgelist, (cost, y+next_y, x+next_x))
        for next_y in range(-2, 3):
            for next_x in range(-2, 3):
                    if 0<=y+next_y<h and 0<=x+next_x<w:
                        if area[y+next_y][x+next_x]=='#': continue
                        if dist[y+next_y][x+next_x]>cost+1:
                            dist[y+next_y][x+next_x] = cost+1
                            heapq.heappush(edgelist, (cost+1, y+next_y, x+next_x))
    return dist

dist = Dijkstra(ch, cw)
if dist[dh][dw] == inf:
    print(-1)
else:
    print(dist[dh][dw])

Fixed submission:
from collections import deque
import sys
input = sys.stdin.readline
h, w = map(int, input().split())
ch, cw = map(int, input().split())
dh, dw = map(int, input().split())
ch-=1; cw-=1; dh-=1; dw-=1
area = [list(input()) for _ in range(h)]
inf = 10**100
dist = [[inf]*w for i in range(h)]

dwalk = [(0, 1), (0, -1), (1, 0), (-1, 0)]

def Dijkstra(ch, cw):
    import heapq
    edgelist = [(0, ch, cw)]
    heapq.heapify(edgelist)
    dist[ch][cw] = 0
    while len(edgelist):
        cost, y, x = heapq.heappop(edgelist)
        if y==dh and x==dw:
            return dist
        if dist[y][x] < cost: continue
        for next_y, next_x in dwalk:
            if 0<=y+next_y<h and 0<=x+next_x<w:
                if area[y+next_y][x+next_x]=='#': continue
                if dist[y+next_y][x+next_x]>cost:
                    dist[y+next_y][x+next_x] = cost
                    heapq.heappush(edgelist, (cost, y+next_y, x+next_x))
        for next_y in range(-2, 3):
            for next_x in range(-2, 3):
                    if 0<=y+next_y<h and 0<=x+next_x<w:
                        if area[y+next_y][x+next_x]=='#': continue
                        if dist[y+next_y][x+next_x]>cost+1:
                            dist[y+next_y][x+next_x] = cost+1
                            heapq.heappush(edgelist, (cost+1, y+next_y, x+next_x))
    return dist

dist = Dijkstra(ch, cw)
if dist[dh][dw] == inf:
    print(-1)
else:
    print(dist[dh][dw])

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())
ch-=1; cw-=1; dh-=1; dw-=1
area = [list(input()) for _ in range(h)]
inf = 10**100
dist = [[inf]*w for i in range(h)]

dwalk = [(0, 1), (0, -1), (1, 0), (-1, 0)]

def Dijkstra(ch, cw):
    import heapq
    edgelist = [(0, ch, cw)]
    heapq.heapify(edgelist)
    dist[ch][cw] = 0
    while len(edgelist):
        cost, y, x = heapq.heappop(edgelist)
        dist[y][x] = cost
        if y==dh and x==dw:
            return dist
        for next_y, next_x in dwalk:
            if 0<=y+next_y<h and 0<=x+next_x<w:
                if area[y+next_y][x+next_x]=='#': continue
                if dist[y+next_y][x+next_x]>cost:
                    dist[y+next_y][x+next_x] = cost
                    heapq.heappush(edgelist, (cost, y+next_y, x+next_x))
        for next_y in range(-2, 3):
            for next_x in range(-2, 3):
                    if 0<=y+next_y<h and 0<=x+next_x<w:
                        if area[y+next_y][x+next_x]=='#': continue
                        if dist[y+next_y][x+next_x]>cost+1:
                            dist[y+next_y][x+next_x] = cost+1
                            heapq.heappush(edgelist, (cost+1, y+next_y, x+next_x))
    return dist

dist = Dijkstra(ch, cw)
if dist[dh][dw] == inf:
    print(-1)
else:
    print(dist[dh][dw])

Fixed submission:
from collections import deque
import sys
input = sys.stdin.readline
h, w = map(int, input().split())
ch, cw = map(int, input().split())
dh, dw = map(int, input().split())
ch-=1; cw-=1; dh-=1; dw-=1
area = [list(input()) for _ in range(h)]
inf = 10**100
dist = [[inf]*w for i in range(h)]

dwalk = [(0, 1), (0, -1), (1, 0), (-1, 0)]

def Dijkstra(ch, cw):
    import heapq
    edgelist = [(0, ch, cw)]
    heapq.heapify(edgelist)
    dist[ch][cw] = 0
    while len(edgelist):
        cost, y, x = heapq.heappop(edgelist)
        if y==dh and x==dw:
            return dist
        if dist[y][x] < cost: continue
        for next_y, next_x in dwalk:
            if 0<=y+next_y<h and 0<=x+next_x<w:
                if area[y+next_y][x+next_x]=='#': continue
                if dist[y+next_y][x+next_x]>cost:
                    dist[y+next_y][x+next_x] = cost
                    heapq.heappush(edgelist, (cost, y+next_y, x+next_x))
        for next_y in range(-2, 3):
            for next_x in range(-2, 3):
                    if 0<=y+next_y<h and 0<=x+next_x<w:
                        if area[y+next_y][x+next_x]=='#': continue
                        if dist[y+next_y][x+next_x]>cost+1:
                            dist[y+next_y][x+next_x] = cost+1
                            heapq.heappush(edgelist, (cost+1, y+next_y, x+next_x))
    return dist

dist = Dijkstra(ch, cw)
if dist[dh][dw] == inf:
    print(-1)
else:
    print(dist[dh][dw])

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())
ch-=1; cw-=1; dh-=1; dw-=1
area = [list(input()) for _ in range(h)]
inf = 10**100
dist = [[inf]*w for i in range(h)]

dwalk = [(0, 1), (0, -1), (1, 0), (-1, 0)]

def Dijkstra(ch, cw):
    import heapq
    edgelist = [(0, ch, cw)]
    heapq.heapify(edgelist)
    dist[ch][cw] = 0
    while len(edgelist):
        cost, y, x = heapq.heappop(edgelist)
        dist[y][x] = cost
        if y==dh and x==dw:
            return dist
        for next_y, next_x in dwalk:
            if 0<=y+next_y<h and 0<=x+next_x<w:
                if area[y+next_y][x+next_x]=='#': continue
                if dist[y+next_y][x+next_x]>cost:
                    dist[y+next_y][x+next_x] = cost
                    heapq.heappush(edgelist, (cost, y+next_y, x+next_x))
        for next_y in range(-2, 3):
            for next_x in range(-2, 3):
                    if 0<=y+next_y<h and 0<=x+next_x<w:
                        if area[y+next_y][x+next_x]=='#': continue
                        if dist[y+next_y][x+next_x]>cost+1:
                            dist[y+next_y][x+next_x] = cost+1
                            heapq.heappush(edgelist, (cost+1, y+next_y, x+next_x))
    return dist

dist = Dijkstra(ch, cw)
if dist[dh][dw] == inf:
    print(-1)
else:
    print(dist[dh][dw])

Fixed submission:
from collections import deque
import sys
input = sys.stdin.readline
h, w = map(int, input().split())
ch, cw = map(int, input().split())
dh, dw = map(int, input().split())
ch-=1; cw-=1; dh-=1; dw-=1
area = [list(input()) for _ in range(h)]
inf = 10**100
dist = [[inf]*w for i in range(h)]

dwalk = [(0, 1), (0, -1), (1, 0), (-1, 0)]

def Dijkstra(ch, cw):
    import heapq
    edgelist = [(0, ch, cw)]
    heapq.heapify(edgelist)
    dist[ch][cw] = 0
    while len(edgelist):
        cost, y, x = heapq.heappop(edgelist)
        if y==dh and x==dw:
            return dist
        if dist[y][x] < cost: continue
        for next_y, next_x in dwalk:
            if 0<=y+next_y<h and 0<=x+next_x<w:
                if area[y+next_y][x+next_x]=='#': continue
                if dist[y+next_y][x+next_x]>cost:
                    dist[y+next_y][x+next_x] = cost
                    heapq.heappush(edgelist, (cost, y+next_y, x+next_x))
        for next_y in range(-2, 3):
            for next_x in range(-2, 3):
                    if 0<=y+next_y<h and 0<=x+next_x<w:
                        if area[y+next_y][x+next_x]=='#': continue
                        if dist[y+next_y][x+next_x]>cost+1:
                            dist[y+next_y][x+next_x] = cost+1
                            heapq.heappush(edgelist, (cost+1, y+next_y, x+next_x))
    return dist

dist = Dijkstra(ch, cw)
if dist[dh][dw] == inf:
    print(-1)
else:
    print(dist[dh][dw])

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())
ch-=1; cw-=1; dh-=1; dw-=1
area = [list(input()) for _ in range(h)]
dist = [[-1]*w for i in range(h)]

dk = [(i, j, 0) for i in range(-2, 3) for j in range(-2, 3)]
d = []
for i, j, c in dk:
    if (i, j) in [(0, 1), (0, -1), (1, 0), (-1, 0)]:
        c = 0
    else:
        c = 1
    d.append((c, i, j))
d.sort()

def Dijkstra(ch, cw):
    """
    Dijkstra法を用いて単一始点終点の最短コストを算出する
    0オリジンとする。
    es: 辺を表す配列。
        es[start]: [cost, en]
    n: 頂点数
    source: 始点
    return: dist　最短距離距離配列。
    """
    import heapq
    used = [[False] * w for i in range(h)] # Falseならば計算対象
    edgelist = []
    # 始点の辺を追加
    for e in d:
        c, y, x = e
        if 0<=ch+y<h and 0<=cw+x<w:
            if used[ch+y][cw+x]: continue
            if area[ch+y][cw+x]=='#': continue
            heapq.heappush(edgelist, (c, ch+y, cw+x))
    used[ch][cw] = True
    dist[ch][cw] = 0
    while len(edgelist):
        minedge = heapq.heappop(edgelist)
        cost, y, x = minedge
        if used[y][x]:
            continue
        dist[y][x] = cost
        used[y][x] = True
        if y==dh and x==dw:
            return dist
        for e in d:
            next_cost, next_y, next_x = e
            if 0<=y+next_y<h and 0<=x+next_x<w:
                if used[y+next_y][x+next_x]: continue
                if area[y+next_y][x+next_x]=='#': continue
                heapq.heappush(edgelist, (dist[y][x]+next_cost, y+next_y, x+next_x))
    return dist

dist = Dijkstra(ch, cw)
print(dist[dh][dw])

Fixed submission:
from collections import deque
import sys
input = sys.stdin.readline
h, w = map(int, input().split())
ch, cw = map(int, input().split())
dh, dw = map(int, input().split())
ch-=1; cw-=1; dh-=1; dw-=1
area = [list(input()) for _ in range(h)]
inf = 10**100
dist = [[inf]*w for i in range(h)]

dwalk = [(0, 1), (0, -1), (1, 0), (-1, 0)]

def Dijkstra(ch, cw):
    import heapq
    edgelist = [(0, ch, cw)]
    heapq.heapify(edgelist)
    dist[ch][cw] = 0
    while len(edgelist):
        cost, y, x = heapq.heappop(edgelist)
        if y==dh and x==dw:
            return dist
        if dist[y][x] < cost: continue
        for next_y, next_x in dwalk:
            if 0<=y+next_y<h and 0<=x+next_x<w:
                if area[y+next_y][x+next_x]=='#': continue
                if dist[y+next_y][x+next_x]>cost:
                    dist[y+next_y][x+next_x] = cost
                    heapq.heappush(edgelist, (cost, y+next_y, x+next_x))
        for next_y in range(-2, 3):
            for next_x in range(-2, 3):
                    if 0<=y+next_y<h and 0<=x+next_x<w:
                        if area[y+next_y][x+next_x]=='#': continue
                        if dist[y+next_y][x+next_x]>cost+1:
                            dist[y+next_y][x+next_x] = cost+1
                            heapq.heappush(edgelist, (cost+1, y+next_y, x+next_x))
    return dist

dist = Dijkstra(ch, cw)
if dist[dh][dw] == inf:
    print(-1)
else:
    print(dist[dh][dw])

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())
ch-=1; cw-=1; dh-=1; dw-=1
area = [list(input()) for _ in range(h)]
dist = [[-1]*w for i in range(h)]

dk = [(i, j, 0) for i in range(-2, 3) for j in range(-2, 3)]
d = []
for i, j, c in dk:
    if (i, j) in [(0, 1), (0, -1), (1, 0), (-1, 0)]:
        c = 0
    else:
        c = 1
    d.append((c, i, j))

def Dijkstra(ch, cw):
    """
    Dijkstra法を用いて単一始点終点の最短コストを算出する
    0オリジンとする。
    es: 辺を表す配列。
        es[start]: [cost, en]
    n: 頂点数
    source: 始点
    return: dist　最短距離距離配列。
    """
    import heapq
    used = [[False] * w for i in range(h)] # Falseならば計算対象
    edgelist = []
    # 始点の辺を追加
    for e in d:
        c, y, x = e
        if 0<=ch+y<h and 0<=cw+x<w:
            if used[ch+y][cw+x]: continue
            if area[ch+y][cw+x]=='#': continue
            heapq.heappush(edgelist, (c, ch+y, cw+x))
    used[ch][cw] = True
    dist[ch][cw] = 0
    while len(edgelist):
        minedge = heapq.heappop(edgelist)
        cost, y, x = minedge
        if used[y][x]:
            continue
        dist[y][x] = cost
        used[y][x] = True
        if y==dh and x==dw:
            return dist
        for e in d:
            next_cost, next_y, next_x = e
            if 0<=y+next_y<h and 0<=x+next_x<w:
                if used[y+next_y][x+next_x]: continue
                if area[y+next_y][x+next_x]=='#': continue
                heapq.heappush(edgelist, (dist[y][x]+next_cost, y+next_y, x+next_x))
    return dist

dist = Dijkstra(ch, cw)
print(dist[dh][dw])

Fixed submission:
from collections import deque
import sys
input = sys.stdin.readline
h, w = map(int, input().split())
ch, cw = map(int, input().split())
dh, dw = map(int, input().split())
ch-=1; cw-=1; dh-=1; dw-=1
area = [list(input()) for _ in range(h)]
inf = 10**100
dist = [[inf]*w for i in range(h)]

dwalk = [(0, 1), (0, -1), (1, 0), (-1, 0)]

def Dijkstra(ch, cw):
    import heapq
    edgelist = [(0, ch, cw)]
    heapq.heapify(edgelist)
    dist[ch][cw] = 0
    while len(edgelist):
        cost, y, x = heapq.heappop(edgelist)
        if y==dh and x==dw:
            return dist
        if dist[y][x] < cost: continue
        for next_y, next_x in dwalk:
            if 0<=y+next_y<h and 0<=x+next_x<w:
                if area[y+next_y][x+next_x]=='#': continue
                if dist[y+next_y][x+next_x]>cost:
                    dist[y+next_y][x+next_x] = cost
                    heapq.heappush(edgelist, (cost, y+next_y, x+next_x))
        for next_y in range(-2, 3):
            for next_x in range(-2, 3):
                    if 0<=y+next_y<h and 0<=x+next_x<w:
                        if area[y+next_y][x+next_x]=='#': continue
                        if dist[y+next_y][x+next_x]>cost+1:
                            dist[y+next_y][x+next_x] = cost+1
                            heapq.heappush(edgelist, (cost+1, y+next_y, x+next_x))
    return dist

dist = Dijkstra(ch, cw)
if dist[dh][dw] == inf:
    print(-1)
else:
    print(dist[dh][dw])

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())
ch-=1; cw-=1; dh-=1; dw-=1
area = [list(input()) for _ in range(h)]
dist = [[-1]*w for i in range(h)]

dk = [(i, j, 0) for i in range(-2, 3) for j in range(-2, 3)]
d = []
for i, j, c in dk:
    if (i, j) in [(0, 1), (0, -1), (1, 0), (-1, 0)]:
        c = 0
    else:
        c = 1
    d.append((c, i, j))

def Dijkstra(ch, cw):
    """
    Dijkstra法を用いて単一始点終点の最短コストを算出する
    0オリジンとする。
    es: 辺を表す配列。
        es[start]: [cost, en]
    n: 頂点数
    source: 始点
    return: dist　最短距離距離配列。
    """
    import heapq
    used = [[False] * w for i in range(h)] # Falseならば計算対象
    edgelist = []
    # 始点の辺を追加
    for e in d:
        c, y, x = e
        if 0<=ch+y<h and 0<=cw+x<w:
            if used[ch+y][cw+x]: continue
            if area[ch+y][cw+x]=='#': continue
            heapq.heappush(edgelist, (c, ch+y, cw+x))
    used[ch][cw] = True
    dist[ch][cw] = 0
    while len(edgelist):
        minedge = heapq.heappop(edgelist)
        cost, y, x = minedge
        if used[y][x]:
            continue
        dist[y][x] = cost
        used[y][x] = True
        for e in d:
            next_cost, next_y, next_x = e
            if 0<=y+next_y<h and 0<=x+next_x<w:
                if used[y+next_y][x+next_x]: continue
                if area[y+next_y][x+next_x]=='#': continue
                heapq.heappush(edgelist, (dist[y][x]+next_cost, y+next_y, x+next_x))
    return dist

dist = Dijkstra(ch, cw)
print(dist[dh][dw])

Fixed submission:
from collections import deque
import sys
input = sys.stdin.readline
h, w = map(int, input().split())
ch, cw = map(int, input().split())
dh, dw = map(int, input().split())
ch-=1; cw-=1; dh-=1; dw-=1
area = [list(input()) for _ in range(h)]
inf = 10**100
dist = [[inf]*w for i in range(h)]

dwalk = [(0, 1), (0, -1), (1, 0), (-1, 0)]

def Dijkstra(ch, cw):
    import heapq
    edgelist = [(0, ch, cw)]
    heapq.heapify(edgelist)
    dist[ch][cw] = 0
    while len(edgelist):
        cost, y, x = heapq.heappop(edgelist)
        if y==dh and x==dw:
            return dist
        if dist[y][x] < cost: continue
        for next_y, next_x in dwalk:
            if 0<=y+next_y<h and 0<=x+next_x<w:
                if area[y+next_y][x+next_x]=='#': continue
                if dist[y+next_y][x+next_x]>cost:
                    dist[y+next_y][x+next_x] = cost
                    heapq.heappush(edgelist, (cost, y+next_y, x+next_x))
        for next_y in range(-2, 3):
            for next_x in range(-2, 3):
                    if 0<=y+next_y<h and 0<=x+next_x<w:
                        if area[y+next_y][x+next_x]=='#': continue
                        if dist[y+next_y][x+next_x]>cost+1:
                            dist[y+next_y][x+next_x] = cost+1
                            heapq.heappush(edgelist, (cost+1, y+next_y, x+next_x))
    return dist

dist = Dijkstra(ch, cw)
if dist[dh][dw] == inf:
    print(-1)
else:
    print(dist[dh][dw])

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())
ch-=1; cw-=1; dh-=1; dw-=1
area = [list(input()) for _ in range(h)]
dist = [[-1]*w for i in range(h)]

dk = [(i, j, 0) for i in range(-2, 3) for j in range(-2, 3)]
d = []
for i, j, c in dk:
    if (i, j) in [(0, 1), (0, -1), (1, 0), (-1, 0)]:
        c = 0
    else:
        c = 1
    d.append((c, i, j))

def Dijkstra(ch, cw):
    """
    Dijkstra法を用いて単一始点終点の最短コストを算出する
    0オリジンとする。
    es: 辺を表す配列。
        es[start]: [cost, en]
    n: 頂点数
    source: 始点
    return: dist　最短距離距離配列。
    """
    import heapq
    used = [[False] * w for i in range(h)] # Falseならば計算対象
    edgelist = []
    # 始点の辺を追加
    for e in d:
        c, y, x = e
        if 0<=ch+y<h and 0<=cw+x<w:
            if used[ch+y][cw+x]: continue
            if area[ch+y][cw+x]=='#': continue
            heapq.heappush(edgelist, (c, ch+y, cw+x))
    used[ch][cw] = True
    dist[ch][cw] = 0
    while len(edgelist):
        minedge = heapq.heappop(edgelist)
        cost, y, x = minedge
        if used[y][x]:
            continue
        dist[y][x] = cost
        used[y][x] = True
        for e in d:
            next_cost, next_y, next_x = e
            if 0<=y+next_y<h and 0<=x+next_x<w:
                if used[y+next_y][x+next_x]: continue
                if area[y+next_y][x+next_x]=='#': continue
                heapq.heappush(edgelist, (dist[y][x]+next_cost, y+next_y, x+next_x))
    return dist

dist = Dijkstra(ch, cw)
print(dist[dh][dw])

Fixed submission:
from collections import deque
import sys
input = sys.stdin.readline
h, w = map(int, input().split())
ch, cw = map(int, input().split())
dh, dw = map(int, input().split())
ch-=1; cw-=1; dh-=1; dw-=1
area = [list(input()) for _ in range(h)]
inf = 10**100
dist = [[inf]*w for i in range(h)]

dwalk = [(0, 1), (0, -1), (1, 0), (-1, 0)]

def Dijkstra(ch, cw):
    import heapq
    edgelist = [(0, ch, cw)]
    heapq.heapify(edgelist)
    dist[ch][cw] = 0
    while len(edgelist):
        cost, y, x = heapq.heappop(edgelist)
        if y==dh and x==dw:
            return dist
        if dist[y][x] < cost: continue
        for next_y, next_x in dwalk:
            if 0<=y+next_y<h and 0<=x+next_x<w:
                if area[y+next_y][x+next_x]=='#': continue
                if dist[y+next_y][x+next_x]>cost:
                    dist[y+next_y][x+next_x] = cost
                    heapq.heappush(edgelist, (cost, y+next_y, x+next_x))
        for next_y in range(-2, 3):
            for next_x in range(-2, 3):
                    if 0<=y+next_y<h and 0<=x+next_x<w:
                        if area[y+next_y][x+next_x]=='#': continue
                        if dist[y+next_y][x+next_x]>cost+1:
                            dist[y+next_y][x+next_x] = cost+1
                            heapq.heappush(edgelist, (cost+1, y+next_y, x+next_x))
    return dist

dist = Dijkstra(ch, cw)
if dist[dh][dw] == inf:
    print(-1)
else:
    print(dist[dh][dw])