Problem p03436 (python)

Fixed submission:
from queue import Queue

#入力
H, W = map(int, input().split())

#lst = [['a']*W for _ in range(H)]
count = 0 #白色のマスの総数
lst = []
row = []
for i in range(H):
    row = list(input())
    count += row.count('.')
    lst += [row]
 
#for i in range(H):
#    for j in range(W):
#        if lst[i][j] == '.':
#            count += 1

#sx, sy = 1, 1 #スタート位置
#gx, gy = H, W #ゴール位置

move = [[-1, 0], [1,0], [0, -1], [0, 1]]

def bfs():
    q = Queue()
    INF = 10 ** 9
    d = [[INF]* W for _ in range(H)]
    q.put(0)
    q.put(0)
    d[0][0] = 0

    while True:
        if q.empty():
            break
        else:
            px = q.get()
            py = q.get()
            if px == H-1 and py == W-1:
                break
            else:
                for dx, dy in move:
                    nx = px + dx
                    ny = py + dy

                    if 0 <= nx and nx < H and 0 <= ny and ny < W and lst[nx][ny] == '.' and d[nx][ny] == INF:
                        q.put(nx)
                        q.put(ny)
                        d[nx][ny] = d[px][py] + 1
    return d[H-1][W-1]

a = bfs()

if a == 10 **9:
    print (-1)
else:
    print (count - a - 1)

Buggy submission (verdict: Runtime Error):
import collections

#入力
H, W = map(int, input().split())

#lst = [['a']*W for _ in range(H)]
count = 0 #白色のマスの総数
lst = []
row = []
for i in range(H):
    row = list(input())
    count += row.count('.')
    lst += [row]
 
#for i in range(H):
#    for j in range(W):
#        if lst[i][j] == '.':
#            count += 1

sx, sy = 1, 1 #スタート位置
gx, gy = H, W #ゴール位置

move = [[-1, 0], [1,0], [0, -1], [0, 1]]

def bfs():
    q = collections.deque()
    INF = 10 ** 9
    d = [[INF]* W for _ in range(H)]
    q.append(0)
    q.append(0)
    d[0][0] = 0

    while True:
        if q.empty():
            break
        px = q.popleft()
        py = q.popleft()
        if px == gx-1 and py == gy-1:
            break
        else:
            for dx, dy in move:
                nx = px + dx
                ny = py + dy

                if 0 <= nx and nx < H and 0 <= ny and ny < W and lst[nx][ny] == '.' and d[nx][ny] == INF:
                    q.append(nx)
                    q.append(ny)
                    d[nx][ny] = d[px][py] + 1
    return d[gx-1][gy-1]

a = bfs()

if a == 10 **9:
    print (-1)
else:
    print (count - a - 1)

Buggy submission (verdict: Runtime Error):
import collections

#入力
H, W = map(int, input().split())

#lst = [['a']*W for _ in range(H)]
count = 0 #白色のマスの総数
lst = []
row = []
for i in range(H):
    row = list(input())
    count += row.count('.')
    lst += [row]
 
#for i in range(H):
#    for j in range(W):
#        if lst[i][j] == '.':
#            count += 1

sx, sy = 1, 1 #スタート位置
gx, gy = H, W #ゴール位置

move = [[-1, 0], [1,0], [0, -1], [0, 1]]

def bfs():
    q = collections.deque()
    INF = 10 ** 3
    d = [[INF]* W for _ in range(H)]
    q.append(0)
    q.append(0)
    d[0][0] = 0

    while True:
        if q.empty():
            break
        px = q.popleft()
        py = q.popleft()
        if px == gx-1 and py == gy-1:
            break
        else:
            for dx, dy in move:
                nx = px + dx
                ny = py + dy

                if 0 <= nx and nx < H and 0 <= ny and ny < W and lst[nx][ny] == '.' and d[nx][ny] == INF:
                    q.append(nx)
                    q.append(ny)
                    d[nx][ny] = d[px][py] + 1
    return d[gx-1][gy-1]

a = bfs()

if a == 10 **9:
    print (-1)
else:
    print (count - a - 1)

Buggy submission (verdict: Runtime Error):
import collections

#入力
H, W = map(int, input().split())

#lst = [['a']*W for _ in range(H)]
count = 0 #白色のマスの総数
lst = []
row = []
for i in range(H):
    row = list(input())
    count += row.count('.')
    lst += [row]
 
#for i in range(H):
#    for j in range(W):
#        if lst[i][j] == '.':
#            count += 1

sx, sy = 1, 1 #スタート位置
gx, gy = H, W #ゴール位置

move = [[-1, 0], [1,0], [0, -1], [0, 1]]

def bfs():
    q = collections.deque()
    INF = 10 ** 3
    d = [[INF]* W for _ in range(H)]
    q.append(0)
    q.append(0)
    d[0][0] = 0

    while True:
        px = q.popleft()
        py = q.popleft()
        if px == gx-1 and py == gy-1:
            break
        else:
            for dx, dy in move:
                nx = px + dx
                ny = py + dy

                if 0 <= nx and nx < H and 0 <= ny and ny < W and lst[nx][ny] == '.' and d[nx][ny] == INF:
                    q.append(nx)
                    q.append(ny)
                    d[nx][ny] = d[px][py] + 1
    return d[gx-1][gy-1]

a = bfs()

if a == 10 **9:
    print (-1)
else:
    print (count - a - 1)