Buggy python submission (verdict: Time Limit Exceeded):
import itertools


h, w = map(int, input().split())
c = [list(map(ord, input())) for i in range(h)]
c = list(itertools.chain.from_iterable(c))
INF = 10 ** 9


ans = 0
dq = [0] * ((h + 1) ** 2)
for wi in range(w - 1):
    for diff in range(h + 1):
        cnt = 0
        for i in range(h - diff):
            cnt += (c[i * w + wi] == c[(i + diff) * w + wi + 1])
        dq[diff * (h + 1)] = cnt
        for i in range(h - diff - 1):
            cnt -= (c[(h - i - 1 - diff) * w + wi] == c[(h - i - 1) * w + wi + 1])
            dq[(i + 1 + diff) * (h + 1) + i + 1] = cnt

        cnt = 0
        for i in range(h - diff):
            cnt += (c[(i + diff) * w + wi] == c[i * w + wi + 1])
        dq[diff] = cnt
        for i in range(h - diff - 1):
            cnt -= (c[(h - i - 1 - diff) * w + wi + 1] == c[(h - i - 1) * w + wi])
            dq[(i + 1) * (h + 1) + i + 1 + diff] = cnt
            
    dp = [INF] * ((h + 1) ** 2)
    dp[0] = 0
    for i in range(h + 1):
        for j in range(h + 1):
            if i + 1 < h + 1:
                dp[(i + 1) * (h + 1) + j] = min(dp[i * (h + 1) + j] + dq[i * (h + 1) + j], dp[(i + 1) *(h + 1) + j])
            if j + 1 < h + 1:
                dp[i * (h + 1) + j + 1] = min(dp[i * (h + 1) + j] + dq[i * (h + 1) + j], dp[i * (h + 1) + j + 1])
    ans += dp[-1]

print(ans)
    

Fixed submission:
def solve(k):
    dp = [[0] * (h + 1) for i in range(h + 1)]
    for i in range(h):
        for diff in range(h - i):
            dp[i + 1][i + 1 + diff] = dp[i][i + diff] + (s[i + diff][k] == s[i][k + 1])
            dp[i + 1 + diff][i + 1] = dp[i + diff][i] + (s[i][k] == s[i + diff][k + 1])

    dq = [[INF] * (h + 1) for i in range(h + 1)]
    dq[0][0] = 0
    for i in range(h):
        dq[i + 1][0] = dq[i][0] + dp[h - i][h]
        dq[0][i + 1] = dq[0][i] + dp[h][h - i]  
    for i in range(h):
        for j in range(h):
            dq[i + 1][j + 1] = min(dq[i + 1][j] + dp[h - (i + 1)][h - j],
                                   dq[i][j + 1] + dp[h - i][h - (j + 1)])

    return dq[h][h]


h, w = map(int, input().split())
s = [input() for i in range(h)]
INF = 10 ** 5
OFFSET = 500

ans = 0
for i in range(w - 1):
    ans += solve(i)
    
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
import itertools


h, w = map(int, input().split())
c = [list(map(ord, input())) for i in range(h)]
c = list(itertools.chain.from_iterable(c))
INF = 10 ** 9


ans = 0
dq = [0] * ((h + 1) ** 2)
for wi in range(w - 1):
    for diff in range(h + 1):
        cnt = 0
        for i in range(h):
            if i + diff >= h:
                break
            cnt += (c[i * w + wi] == c[(i + diff) * w + wi + 1])
        dq[(0 + diff) * (h + 1) + 0] = cnt
        for i in range(h):
            if i + 1 + diff >= h:
                break
            cnt -= (c[(h - i - 1 - diff) * w + wi] == c[(h - i - 1) * w + wi + 1])
            dq[(i + 1 + diff) * (h + 1) + i + 1] = cnt

        cnt = 0
        for i in range(h):
            if i + diff >= h:
                break
            cnt += (c[(i + diff) * w + wi] == c[i * w + wi + 1])
        dq[0 + diff] = cnt
        for i in range(h):
            if i + 1 + diff >= h:
                break
            cnt -= (c[(h - i - 1 - diff) * w + wi + 1] == c[(h - i - 1) * w + wi])
            dq[(i + 1) * (h + 1) + i + 1 + diff] = cnt
            
    dp = [INF] * ((h + 1) ** 2)
    dp[0] = 0
    for i in range(h + 1):
        for j in range(h + 1):
            if i + 1 < h + 1:
                dp[(i + 1) *(h + 1) + j] = min(dp[i * (h + 1) + j] + dq[i * (h + 1) + j], dp[(i + 1) *(h + 1) + j])
            if j + 1 < h + 1:
                dp[i * (h + 1) + j + 1] = min(dp[i * (h + 1) + j] + dq[i * (h + 1) + j], dp[i * (h + 1) + j + 1])
    ans += dp[-1]

print(ans)
    

Fixed submission:
def solve(k):
    dp = [[0] * (h + 1) for i in range(h + 1)]
    for i in range(h):
        for diff in range(h - i):
            dp[i + 1][i + 1 + diff] = dp[i][i + diff] + (s[i + diff][k] == s[i][k + 1])
            dp[i + 1 + diff][i + 1] = dp[i + diff][i] + (s[i][k] == s[i + diff][k + 1])

    dq = [[INF] * (h + 1) for i in range(h + 1)]
    dq[0][0] = 0
    for i in range(h):
        dq[i + 1][0] = dq[i][0] + dp[h - i][h]
        dq[0][i + 1] = dq[0][i] + dp[h][h - i]  
    for i in range(h):
        for j in range(h):
            dq[i + 1][j + 1] = min(dq[i + 1][j] + dp[h - (i + 1)][h - j],
                                   dq[i][j + 1] + dp[h - i][h - (j + 1)])

    return dq[h][h]


h, w = map(int, input().split())
s = [input() for i in range(h)]
INF = 10 ** 5
OFFSET = 500

ans = 0
for i in range(w - 1):
    ans += solve(i)
    
print(ans)

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


h, w = map(int, input().split())
c = [list(map(ord, input())) for i in range(h)]
INF = 10 ** 9


ans = 0
dq = [0] * ((h + 1) ** 2)
for wi in range(w - 1):
    for diff in range(h + 1):
        cnt = 0
        for i in range(h):
            if i + diff >= h:
                break
            cnt += (c[i][wi] == c[i + diff][wi + 1])
        dq[(0 + diff) * (h + 1) + 0] = cnt
        for i in range(h):
            if i + 1 + diff >= h:
                break
            cnt -= (c[h - i - 1 - diff][wi] == c[h - i - 1][wi + 1])
            dq[(i + 1 + diff) * (h + 1) + i + 1] = cnt

        cnt = 0
        for i in range(h):
            if i + diff >= h:
                break
            cnt += (c[i + diff][wi] == c[i][wi + 1])
        dq[0 + diff] = cnt
        for i in range(h):
            if i + 1 + diff >= h:
                break
            cnt -= (c[h - i - 1 - diff][wi + 1] == c[h - i - 1][wi])
            dq[(i + 1) * (h + 1) + i + 1 + diff] = cnt
            
    dp = [INF] * ((h + 1) ** 2)
    dp[0] = 0
    for i in range(h + 1):
        for j in range(h + 1):
            if i + 1 < h + 1:
                dp[(i + 1) *(h + 1) + j] = min(dp[i * (h + 1) + j] + dq[i * (h + 1) + j], dp[(i + 1) *(h + 1) + j])
            if j + 1 < h + 1:
                dp[i * (h + 1) + j + 1] = min(dp[i * (h + 1) + j] + dq[i * (h + 1) + j], dp[i * (h + 1) + j + 1])
    ans += dp[-1]

print(ans)

Fixed submission:
def solve(k):
    dp = [[0] * (h + 1) for i in range(h + 1)]
    for i in range(h):
        for diff in range(h - i):
            dp[i + 1][i + 1 + diff] = dp[i][i + diff] + (s[i + diff][k] == s[i][k + 1])
            dp[i + 1 + diff][i + 1] = dp[i + diff][i] + (s[i][k] == s[i + diff][k + 1])

    dq = [[INF] * (h + 1) for i in range(h + 1)]
    dq[0][0] = 0
    for i in range(h):
        dq[i + 1][0] = dq[i][0] + dp[h - i][h]
        dq[0][i + 1] = dq[0][i] + dp[h][h - i]  
    for i in range(h):
        for j in range(h):
            dq[i + 1][j + 1] = min(dq[i + 1][j] + dp[h - (i + 1)][h - j],
                                   dq[i][j + 1] + dp[h - i][h - (j + 1)])

    return dq[h][h]


h, w = map(int, input().split())
s = [input() for i in range(h)]
INF = 10 ** 5
OFFSET = 500

ans = 0
for i in range(w - 1):
    ans += solve(i)
    
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
h, w = map(int, input().split())
c = [list(map(ord, input())) for i in range(h)]
INF = 10 ** 9


ans = 0
dq = [[0] * (h + 1) for i in range(h + 1)]
dp = [[INF] * (h + 1) for i in range(h + 1)]
for wi in range(w - 1):
    for diff in range(h + 1):
        cnt = 0
        for i in range(h):
            if i + diff >= h:
                break
            cnt += (c[i][wi] == c[i + diff][wi + 1])
        dq[0 + diff][0] = cnt
        for i in range(h):
            if i + 1 + diff >= h:
                break
            cnt -= (c[h - i - 1 - diff][wi] == c[h - i - 1][wi + 1])
            dq[i + 1 + diff][i + 1] = cnt

        cnt = 0
        for i in range(h):
            if i + diff >= h:
                break
            cnt += (c[i + diff][wi] == c[i][wi + 1])
        dq[0][0 + diff] = cnt
        for i in range(h):
            if i + 1 + diff >= h:
                break
            cnt -= (c[h - i - 1 - diff][wi + 1] == c[h - i - 1][wi])
            dq[i + 1][i + 1 + diff] = cnt
            
    for i in range(h + 1):
        for j in range(h + 1):
            dp[i][j] = INF
    dp[0][0] = 0
    for i in range(h + 1):
        for j in range(h + 1):
            if i + 1 < h + 1:
                dp[i + 1][j] = min(dp[i][j] + dq[i][j], dp[i + 1][j])
            if j + 1 < h + 1:
                dp[i][j + 1] = min(dp[i][j] + dq[i][j], dp[i][j + 1])
    ans += dp[-1][-1]

print(ans)
    

Fixed submission:
def solve(k):
    dp = [[0] * (h + 1) for i in range(h + 1)]
    for i in range(h):
        for diff in range(h - i):
            dp[i + 1][i + 1 + diff] = dp[i][i + diff] + (s[i + diff][k] == s[i][k + 1])
            dp[i + 1 + diff][i + 1] = dp[i + diff][i] + (s[i][k] == s[i + diff][k + 1])

    dq = [[INF] * (h + 1) for i in range(h + 1)]
    dq[0][0] = 0
    for i in range(h):
        dq[i + 1][0] = dq[i][0] + dp[h - i][h]
        dq[0][i + 1] = dq[0][i] + dp[h][h - i]  
    for i in range(h):
        for j in range(h):
            dq[i + 1][j + 1] = min(dq[i + 1][j] + dp[h - (i + 1)][h - j],
                                   dq[i][j + 1] + dp[h - i][h - (j + 1)])

    return dq[h][h]


h, w = map(int, input().split())
s = [input() for i in range(h)]
INF = 10 ** 5
OFFSET = 500

ans = 0
for i in range(w - 1):
    ans += solve(i)
    
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
h, w = map(int, input().split())
c = [input() for i in range(h)]
INF = 10 ** 9


ans = 0
dq = [[0] * (h + 1) for i in range(h + 1)]
dp = [[INF] * (h + 1) for i in range(h + 1)]
for wi in range(w - 1):
    for diff in range(h + 1):
        cnt = 0
        for i in range(h):
            if i + diff >= h:
                break
            cnt += (c[i][wi] == c[i + diff][wi + 1])
        dq[0 + diff][0] = cnt
        for i in range(h):
            if i + 1 + diff >= h:
                break
            dq[i + 1 + diff][i + 1] = dq[i + diff][i] - (c[h - i - 1 - diff][wi] == c[h - i - 1][wi + 1])
            
        cnt = 0
        for i in range(h):
            if i + diff >= h:
                break
            cnt += (c[i + diff][wi] == c[i][wi + 1])
        dq[0][0 + diff] = cnt
        for i in range(h):
            if i + 1 + diff >= h:
                break
            dq[i + 1][i + 1 + diff] = dq[i][i + diff] - (c[h - i - 1 - diff][wi + 1] == c[h - i - 1][wi])  
    for i in range(h + 1):
        for j in range(h + 1):
            dp[i][j] = INF
    dp[0][0] = 0
    for i in range(h + 1):
        for j in range(h + 1):
            if i + 1 < h + 1:
                dp[i + 1][j] = min(dp[i][j] + dq[i][j], dp[i + 1][j])
            if j + 1 < h + 1:
                dp[i][j + 1] = min(dp[i][j] + dq[i][j], dp[i][j + 1])
    ans += dp[-1][-1]

print(ans)
    

Fixed submission:
def solve(k):
    dp = [[0] * (h + 1) for i in range(h + 1)]
    for i in range(h):
        for diff in range(h - i):
            dp[i + 1][i + 1 + diff] = dp[i][i + diff] + (s[i + diff][k] == s[i][k + 1])
            dp[i + 1 + diff][i + 1] = dp[i + diff][i] + (s[i][k] == s[i + diff][k + 1])

    dq = [[INF] * (h + 1) for i in range(h + 1)]
    dq[0][0] = 0
    for i in range(h):
        dq[i + 1][0] = dq[i][0] + dp[h - i][h]
        dq[0][i + 1] = dq[0][i] + dp[h][h - i]  
    for i in range(h):
        for j in range(h):
            dq[i + 1][j + 1] = min(dq[i + 1][j] + dp[h - (i + 1)][h - j],
                                   dq[i][j + 1] + dp[h - i][h - (j + 1)])

    return dq[h][h]


h, w = map(int, input().split())
s = [input() for i in range(h)]
INF = 10 ** 5
OFFSET = 500

ans = 0
for i in range(w - 1):
    ans += solve(i)
    
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
h, w = map(int, input().split())
c = [input() for i in range(h)]
INF = 10 ** 9


ans = 0
for wi in range(w - 1):
    dq = [[0] * (h + 1) for i in range(h + 1)]
    for diff in range(h + 1):
        cnt = 0
        for i in range(h):
            if i + diff >= h:
                break
            if c[i][wi] == c[i + diff][wi + 1]:
                cnt += 1
        dq[0 + diff][0] = cnt
        for i in range(h):
            if i + 1 + diff >= h:
                break
            dq[i + 1 + diff][i + 1] = dq[i + diff][i] - (c[h - i - 1 - diff][wi] == c[h - i - 1][wi + 1])
            
        cnt = 0
        for i in range(h):
            if i + diff >= h:
                break
            if c[i + diff][wi] == c[i][wi + 1]:
                cnt += 1
        dq[0][0 + diff] = cnt
        for i in range(h):
            if i + 1 + diff >= h:
                break
            dq[i + 1][i + 1 + diff] = dq[i][i + diff] - (c[h - i - 1 - diff][wi + 1] == c[h - i - 1][wi])  
    
    dp = [[INF] * (h + 1) for i in range(h + 1)]
    dp[0][0] = 0
    for i in range(h + 1):
        for j in range(h + 1):
            if i + 1 < h + 1:
                dp[i + 1][j] = min(dp[i][j] + dq[i][j], dp[i + 1][j])
            if j + 1 < h + 1:
                dp[i][j + 1] = min(dp[i][j] + dq[i][j], dp[i][j + 1])
    ans += dp[-1][-1]

print(ans)
    

Fixed submission:
def solve(k):
    dp = [[0] * (h + 1) for i in range(h + 1)]
    for i in range(h):
        for diff in range(h - i):
            dp[i + 1][i + 1 + diff] = dp[i][i + diff] + (s[i + diff][k] == s[i][k + 1])
            dp[i + 1 + diff][i + 1] = dp[i + diff][i] + (s[i][k] == s[i + diff][k + 1])

    dq = [[INF] * (h + 1) for i in range(h + 1)]
    dq[0][0] = 0
    for i in range(h):
        dq[i + 1][0] = dq[i][0] + dp[h - i][h]
        dq[0][i + 1] = dq[0][i] + dp[h][h - i]  
    for i in range(h):
        for j in range(h):
            dq[i + 1][j + 1] = min(dq[i + 1][j] + dp[h - (i + 1)][h - j],
                                   dq[i][j + 1] + dp[h - i][h - (j + 1)])

    return dq[h][h]


h, w = map(int, input().split())
s = [input() for i in range(h)]
INF = 10 ** 5
OFFSET = 500

ans = 0
for i in range(w - 1):
    ans += solve(i)
    
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
def solve(k):
    dp = [[0] * (h + 1) for i in range(h + 1)]
    for i in range(h):
        for diff in range(h - i):
            dp[i + 1][i + 1 + diff] = dp[i][i + diff] + (s[i + diff][k] == s[i][k + 1])
            dp[i + 1 + diff][i + 1] = dp[i + diff][i] + (s[i][k] == s[i + diff][k + 1])
    
    min_cost = {}
    def solve_cost(i, j):
        if i * offset + j in min_cost:
            return min_cost[i * offset + j]
        if i == 0 or j == 0:
            return 0
        min_cost[i * offset + j] = min(solve_cost(i, j - 1), solve_cost(i - 1, j)) + dp[i][j]
        return min_cost[i * offset + j]
    
    return solve_cost(h, h)


h, w = map(int, input().split())
s = [input() for i in range(h)]
offset = 500

ans = 0
for i in range(w - 1):
    ans += solve(i)
    
print(ans)

Fixed submission:
def solve(k):
    dp = [[0] * (h + 1) for i in range(h + 1)]
    for i in range(h):
        for diff in range(h - i):
            dp[i + 1][i + 1 + diff] = dp[i][i + diff] + (s[i + diff][k] == s[i][k + 1])
            dp[i + 1 + diff][i + 1] = dp[i + diff][i] + (s[i][k] == s[i + diff][k + 1])

    dq = [[INF] * (h + 1) for i in range(h + 1)]
    dq[0][0] = 0
    for i in range(h):
        dq[i + 1][0] = dq[i][0] + dp[h - i][h]
        dq[0][i + 1] = dq[0][i] + dp[h][h - i]  
    for i in range(h):
        for j in range(h):
            dq[i + 1][j + 1] = min(dq[i + 1][j] + dp[h - (i + 1)][h - j],
                                   dq[i][j + 1] + dp[h - i][h - (j + 1)])

    return dq[h][h]


h, w = map(int, input().split())
s = [input() for i in range(h)]
INF = 10 ** 5
OFFSET = 500

ans = 0
for i in range(w - 1):
    ans += solve(i)
    
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
def solve(k):
    dp = [[0] * (h + 1) for i in range(h + 1)]
    for i in range(h):
        for diff in range(h - i):
            dp[i + 1][i + 1 + diff] = dp[i][i + diff] + (s[i + diff][k] == s[i][k + 1])
            dp[i + 1 + diff][i + 1] = dp[i + diff][i] + (s[i][k] == s[i + diff][k + 1])
    
    min_cost = {}
    def solve_cost(i, j):
        if (i, j) in min_cost:
            return min_cost[i, j]
        if i == 0 or j == 0:
            return 0
        min_cost[i, j] = min(solve_cost(i, j - 1), solve_cost(i - 1, j)) + dp[i][j]
        return min_cost[i, j]
    
    return solve_cost(h, h)
  
h, w = map(int, input().split())
s = [input() for i in range(h)]

ans = 0
for i in range(w - 1):
    ans += solve(i)
    
print(ans)

Fixed submission:
def solve(k):
    dp = [[0] * (h + 1) for i in range(h + 1)]
    for i in range(h):
        for diff in range(h - i):
            dp[i + 1][i + 1 + diff] = dp[i][i + diff] + (s[i + diff][k] == s[i][k + 1])
            dp[i + 1 + diff][i + 1] = dp[i + diff][i] + (s[i][k] == s[i + diff][k + 1])

    dq = [[INF] * (h + 1) for i in range(h + 1)]
    dq[0][0] = 0
    for i in range(h):
        dq[i + 1][0] = dq[i][0] + dp[h - i][h]
        dq[0][i + 1] = dq[0][i] + dp[h][h - i]  
    for i in range(h):
        for j in range(h):
            dq[i + 1][j + 1] = min(dq[i + 1][j] + dp[h - (i + 1)][h - j],
                                   dq[i][j + 1] + dp[h - i][h - (j + 1)])

    return dq[h][h]


h, w = map(int, input().split())
s = [input() for i in range(h)]
INF = 10 ** 5
OFFSET = 500

ans = 0
for i in range(w - 1):
    ans += solve(i)
    
print(ans)