Buggy python submission (verdict: Runtime Error):
import itertools

H,W = map(int,input().split())
S = [list(input()) for _ in range(H)]

VALID = [[False] * W for _ in range(H)]

def dfs(h,w,parent):
  if parent:
    VALID[h][w] = True

  nxt = [-1,0,1]
  for x,y in itertools.product(nxt,repeat=2):
    if not (abs(x) + abs(y) == 1):
      continue
    nx = h + x
    ny = w + y
    if 0 <= nx < H and 0 <= ny < W and S[nx][ny] == '#' and not VALID[nx][ny]:
      if not parent:
        VALID[h][w] = True
      dfs(nx,ny,True)
        
for i in range(H):
  for j in range(W):
    if S[i][j] == '.':
      VALID[i][j] = True
    else:
      if not VALID[i][j]:
        dfs(i,j,False)
        
if all(sum(VALID,[])):
  print('Yes')
else:
  print('No')


Fixed submission:
import itertools

H,W = map(int,input().split())
S = [list(input()) for _ in range(H)]

ok = True        
for i in range(H):
  for j in range(W):
    if S[i][j] == '#':
      flg = False
      for x,y in itertools.product([-1,0,1],repeat=2):
        if not (abs(x) + abs(y) == 1):
          continue
        nx = i + x;ny = j + y
        if 0 <= nx < H and 0 <= ny < W:
          if S[nx][ny] == '#':
            flg = True
      if not flg:
        ok = False
        break
if ok:
  print('Yes')
else:
  print('No')

Buggy python submission (verdict: Runtime Error):
import itertools

H,W = map(int,input().split())
S = [list(input()) for _ in range(H)]

VALID = [[False] * W for _ in range(H)]

def dfs(h,w,parent):
  if parent:
    VALID[h][w] = True

  nxt = [-1,0,1]
  ok = False
  for x,y in itertools.product(nxt,repeat=2):
    if not (abs(x) + abs(y) == 1):
      continue
    nx = h + x
    ny = w + y
    if 0 <= nx < H and 0 <= ny < W and S[nx][ny] == '#' and not VALID[nx][ny]:
      if not ok:
        ok = True
        VALID[h][w] = True
      dfs(nx,ny,True)
  
  if not parent and ok:
    VALID[h][w] = True
      
for i in range(H):
  for j in range(W):
    if S[i][j] == '.':
      VALID[i][j] = True
    else:
      if not VALID[i][j]:
        dfs(i,j,False)
        
if all(sum(VALID,[])):
  print('Yes')
else:
  print('No')


Fixed submission:
import itertools

H,W = map(int,input().split())
S = [list(input()) for _ in range(H)]

ok = True        
for i in range(H):
  for j in range(W):
    if S[i][j] == '#':
      flg = False
      for x,y in itertools.product([-1,0,1],repeat=2):
        if not (abs(x) + abs(y) == 1):
          continue
        nx = i + x;ny = j + y
        if 0 <= nx < H and 0 <= ny < W:
          if S[nx][ny] == '#':
            flg = True
      if not flg:
        ok = False
        break
if ok:
  print('Yes')
else:
  print('No')

Buggy python submission (verdict: Runtime Error):
import itertools

H,W = map(int,input().split())
S = [list(input()) for _ in range(H)]

VALID = [[False] * W for _ in range(H)]

def dfs(h,w,parent):
  if parent:
    VALID[h][w] = True

  nxt = [-1,0,1]
  ok = False
  for x,y in itertools.product(nxt,repeat=2):
    if not (abs(x) + abs(y) == 1):
      continue
    nx = h + x
    ny = w + y
    if 0 <= nx < H and 0 <= ny < W and S[nx][ny] == '#' and not VALID[nx][ny]:
      ok = True
      dfs(nx,ny,True)
  
  if not parent and ok:
    VALID[h][w] = True
      
for i in range(H):
  for j in range(W):
    if S[i][j] == '.':
      VALID[i][j] = True
    else:
      if not VALID[i][j]:
        dfs(i,j,False)
        
if all(sum(VALID,[])):
  print('Yes')
else:
  print('No')


Fixed submission:
import itertools

H,W = map(int,input().split())
S = [list(input()) for _ in range(H)]

ok = True        
for i in range(H):
  for j in range(W):
    if S[i][j] == '#':
      flg = False
      for x,y in itertools.product([-1,0,1],repeat=2):
        if not (abs(x) + abs(y) == 1):
          continue
        nx = i + x;ny = j + y
        if 0 <= nx < H and 0 <= ny < W:
          if S[nx][ny] == '#':
            flg = True
      if not flg:
        ok = False
        break
if ok:
  print('Yes')
else:
  print('No')

Buggy python submission (verdict: Runtime Error):
import itertools

H,W = map(int,input().split())
S = [list(input()) for _ in range(H)]

VALID = [[False] * W for _ in range(H)]

def dfs(h,w,parent):
  if parent:
    VALID[h][w] = True

  nxt = [-1,0,1]
  ok = False
  for x,y in itertools.product(nxt,repeat=2):
    if not (abs(x) + abs(y) == 1):
      continue
    nx = h + x
    ny = w + y
    if 0 <= nx < H and 0 <= ny < W and S[nx][ny] == '#':
      ok = True
      dfs(nx,ny,True)
  
  if not parent and ok:
    VALID[h][w] = True
      
for i in range(H):
  for j in range(W):
    if S[i][j] == '.':
      VALID[i][j] = True
    else:
      if not VALID[i][j]:
        dfs(i,j,False)
        
if all(sum(VALID,[])):
  print('Yes')
else:
  print('No')


Fixed submission:
import itertools

H,W = map(int,input().split())
S = [list(input()) for _ in range(H)]

ok = True        
for i in range(H):
  for j in range(W):
    if S[i][j] == '#':
      flg = False
      for x,y in itertools.product([-1,0,1],repeat=2):
        if not (abs(x) + abs(y) == 1):
          continue
        nx = i + x;ny = j + y
        if 0 <= nx < H and 0 <= ny < W:
          if S[nx][ny] == '#':
            flg = True
      if not flg:
        ok = False
        break
if ok:
  print('Yes')
else:
  print('No')

Buggy python submission (verdict: Runtime Error):
import itertools

H,W = map(int,input().split())
S = [list(map(int,input().split())) for _ in range(H)]

VALID = [[False] * W for _ in range(H)]

def dfs(h,w,parent):
  if parent:
    VALID[h][w] = True

  nxt = [-1,0,1]
  ok = False
  for x,y in itertools.product(nxt,repeat=2):
    if not (abs(x) + abs(y) == 1):
      continue
    nx = h + x
    ny = w + y
    if 0 <= nx < H and 0 <= ny < W and S[nx][ny] == '#':
      ok = True
      dfs(nx,ny,True)
  
  if not parent and ok:
    VALID[h][w] = True
      
for i in range(H):
  for j in range(W):
    if S[i][j] == '.':
      VALID[i][j] = True
    else:
      if not VALID[i][j]:
        dfs(i,j,False)
        
if all(sum(VALID,[])):
  print('Yes')
else:
  print('No')

Fixed submission:
import itertools

H,W = map(int,input().split())
S = [list(input()) for _ in range(H)]

ok = True        
for i in range(H):
  for j in range(W):
    if S[i][j] == '#':
      flg = False
      for x,y in itertools.product([-1,0,1],repeat=2):
        if not (abs(x) + abs(y) == 1):
          continue
        nx = i + x;ny = j + y
        if 0 <= nx < H and 0 <= ny < W:
          if S[nx][ny] == '#':
            flg = True
      if not flg:
        ok = False
        break
if ok:
  print('Yes')
else:
  print('No')