Buggy python submission (verdict: Runtime Error):
zimport numpy as np
h, w = map(int, input().split())
s = [input() for _ in range(h)]

dp = np.zeros(h * w).reshape(h, w)

if s[0][0] == "#":
    dp[0][0] = 1
else:
    dp[0][0] = 0
    
for i in range(h - 1):
    if s[i + 1][0] == "." or s[i][0] == s[i + 1][0]:
        dp[i + 1][0] = dp[i][0]
    else:
        dp[i + 1][0] = dp[i][0] + 1
for j in range(w - 1):
    if s[0][j + 1] == "." or s[0][j] == s[0][j + 1]:
        dp[0][j + 1] = dp[0][j]
    else:
        dp[0][j + 1] = dp[0][j] + 1

for i in range(h - 1):
    for j in range(w - 1):
        if s[i + 1][j + 1] == "." or (s[i][j + 1] == s[i + 1][j + 1] and s[i + 1][j + 1] == s[i + 1][j]):
            dp[i + 1][j + 1] = min(dp[i][j + 1], dp[i + 1][j])
        elif s[i][j + 1] == s[i + 1][j + 1] and s[i + 1][j + 1] != s[i + 1][j]:
            dp[i + 1][j + 1] = min(dp[i][j + 1], dp[i + 1][j] + 1)
        elif s[i][j + 1] != s[i + 1][j + 1] and s[i + 1][j + 1] == s[i + 1][j]:
            dp[i + 1][j + 1] = min(dp[i][j + 1] + 1, dp[i + 1][j])
        else:
            dp[i + 1][j + 1] = min(dp[i][j + 1] + 1, dp[i + 1][j] + 1)
    
if s[h - 1][w - 1] == "#" and (s[0][0] == "#" and dp[h - 2][w - 1] != 1 and dp[h - 1][w - 2] != 1):
    dp[h- 1][w - 1] += 1

print(int(dp[h - 1][w - 1]))

Fixed submission:
import numpy as np
h, w = map(int, input().split())
s = [input() for _ in range(h)]

dp = np.zeros(h * w).reshape(h, w)

if s[0][0] == "#":
    dp[0][0] = 1
else:
    dp[0][0] = 0
    
for i in range(h - 1):
    if s[i + 1][0] == "." or s[i][0] == s[i + 1][0]:
        dp[i + 1][0] = dp[i][0]
    else:
        dp[i + 1][0] = dp[i][0] + 1
for j in range(w - 1):
    if s[0][j + 1] == "." or s[0][j] == s[0][j + 1]:
        dp[0][j + 1] = dp[0][j]
    else:
        dp[0][j + 1] = dp[0][j] + 1

for i in range(h - 1):
    for j in range(w - 1):
        if s[i + 1][j + 1] == "." or (s[i][j + 1] == s[i + 1][j + 1] and s[i + 1][j + 1] == s[i + 1][j]):
            dp[i + 1][j + 1] = min(dp[i][j + 1], dp[i + 1][j])
        elif s[i][j + 1] == s[i + 1][j + 1] and s[i + 1][j + 1] != s[i + 1][j]:
            dp[i + 1][j + 1] = min(dp[i][j + 1], dp[i + 1][j] + 1)
        elif s[i][j + 1] != s[i + 1][j + 1] and s[i + 1][j + 1] == s[i + 1][j]:
            dp[i + 1][j + 1] = min(dp[i][j + 1] + 1, dp[i + 1][j])
        else:
            dp[i + 1][j + 1] = min(dp[i][j + 1] + 1, dp[i + 1][j] + 1)
  
# if h == 1 and w == 1:
#     if s[0][0] == "#":
#         dp[0][0] == 1
#     else:
#         dp[0][0] == 0
# elif h == 1:
#     if s[h - 1][w - 1] == "#" and (s[0][0] == "#" and dp[h - 1][w - 2] != 1):
#         dp[h- 1][w - 1] += 1
# elif w == 1:
#     if s[h - 1][w - 1] == "#" and (s[0][0] == "#" and dp[h - 2][w - 1] != 1):
#         dp[h- 1][w - 1] += 1
# else:
#     if s[h - 1][w - 1] == "#" and (s[0][0] == "#" and (dp[h - 2][w - 1] != 1 and dp[h - 1][w - 2] != 1)):
#         dp[h- 1][w - 1] += 1
        
# for i in range(w):
#     print(dp[0][i])

print(int(dp[h - 1][w - 1]))

Buggy python submission (verdict: Runtime Error):
import numpy
h, w = map(int, input().split())
s = [input() for _ in range(h)]

dp = np.zeros(h * w).reshape(h, w)

if s[0][0] == "#":
    dp[0][0] = 1
else:
    dp[0][0] = 0
    
for i in range(h - 1):
    if s[i + 1][0] == "." or s[i][0] == s[i + 1][0]:
        dp[i + 1][0] = dp[i][0]
    else:
        dp[i + 1][0] = dp[i][0] + 1
for j in range(w - 1):
    if s[0][j + 1] == "." or s[0][j] == s[0][j + 1]:
        dp[0][j + 1] = dp[0][j]
    else:
        dp[0][j + 1] = dp[0][j] + 1

for i in range(h - 1):
    for j in range(w - 1):
        if s[i + 1][j + 1] == "." or (s[i][j + 1] == s[i + 1][j + 1] and s[i + 1][j + 1] == s[i + 1][j]):
            dp[i + 1][j + 1] = min(dp[i][j + 1], dp[i + 1][j])
        elif s[i][j + 1] == s[i + 1][j + 1] and s[i + 1][j + 1] != s[i + 1][j]:
            dp[i + 1][j + 1] = min(dp[i][j + 1], dp[i + 1][j] + 1)
        elif s[i][j + 1] != s[i + 1][j + 1] and s[i + 1][j + 1] == s[i + 1][j]:
            dp[i + 1][j + 1] = min(dp[i][j + 1] + 1, dp[i + 1][j])
        else:
            dp[i + 1][j + 1] = min(dp[i][j + 1] + 1, dp[i + 1][j] + 1)
    
if s[h - 1][w - 1] == "#" and (dp[h - 2][w - 1] != 1 and dp[h - 2][w - 1] != 1):
    dp[h- 1][w - 1] += 1

print(int(dp[h - 1][w - 1]))

Fixed submission:
import numpy as np
h, w = map(int, input().split())
s = [input() for _ in range(h)]

dp = np.zeros(h * w).reshape(h, w)

if s[0][0] == "#":
    dp[0][0] = 1
else:
    dp[0][0] = 0
    
for i in range(h - 1):
    if s[i + 1][0] == "." or s[i][0] == s[i + 1][0]:
        dp[i + 1][0] = dp[i][0]
    else:
        dp[i + 1][0] = dp[i][0] + 1
for j in range(w - 1):
    if s[0][j + 1] == "." or s[0][j] == s[0][j + 1]:
        dp[0][j + 1] = dp[0][j]
    else:
        dp[0][j + 1] = dp[0][j] + 1

for i in range(h - 1):
    for j in range(w - 1):
        if s[i + 1][j + 1] == "." or (s[i][j + 1] == s[i + 1][j + 1] and s[i + 1][j + 1] == s[i + 1][j]):
            dp[i + 1][j + 1] = min(dp[i][j + 1], dp[i + 1][j])
        elif s[i][j + 1] == s[i + 1][j + 1] and s[i + 1][j + 1] != s[i + 1][j]:
            dp[i + 1][j + 1] = min(dp[i][j + 1], dp[i + 1][j] + 1)
        elif s[i][j + 1] != s[i + 1][j + 1] and s[i + 1][j + 1] == s[i + 1][j]:
            dp[i + 1][j + 1] = min(dp[i][j + 1] + 1, dp[i + 1][j])
        else:
            dp[i + 1][j + 1] = min(dp[i][j + 1] + 1, dp[i + 1][j] + 1)
  
# if h == 1 and w == 1:
#     if s[0][0] == "#":
#         dp[0][0] == 1
#     else:
#         dp[0][0] == 0
# elif h == 1:
#     if s[h - 1][w - 1] == "#" and (s[0][0] == "#" and dp[h - 1][w - 2] != 1):
#         dp[h- 1][w - 1] += 1
# elif w == 1:
#     if s[h - 1][w - 1] == "#" and (s[0][0] == "#" and dp[h - 2][w - 1] != 1):
#         dp[h- 1][w - 1] += 1
# else:
#     if s[h - 1][w - 1] == "#" and (s[0][0] == "#" and (dp[h - 2][w - 1] != 1 and dp[h - 1][w - 2] != 1)):
#         dp[h- 1][w - 1] += 1
        
# for i in range(w):
#     print(dp[0][i])

print(int(dp[h - 1][w - 1]))