[B1018][체스판 다시 칠하기][python]

https://www.acmicpc.net/problem/1018

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n, m = map(int, input().split())
m_list = []
for _ in range(n):
    m_list.append(input())
n_min = 64

for i in range(n - 7):
    for j in range(m - 7):
        cnt1 = 0
        cnt2 = 0
        for k in range(i, i + 8):
            for s in range(j, j + 8):
                if k % 2 == 0 and s % 2 == 0:
                    if m_list[k][s] == 'B':
                        cnt1 += 1
                elif k % 2 == 1 and s % 2 == 1:
                    if m_list[k][s] == 'B':
                        cnt1 += 1
                elif k % 2 == 0 and s % 2 == 1:
                    if m_list[k][s] == 'W':
                        cnt1 += 1
                elif k % 2 == 1 and s % 2 == 0:
                    if m_list[k][s] == 'W':
                        cnt1 += 1
        for k in range(i, i + 8):
            for s in range(j, j + 8):
                if k % 2 == 0 and s % 2 == 0:
                    if m_list[k][s] == 'W':
                        cnt2 += 1
                elif k % 2 == 1 and s % 2 == 1:
                    if m_list[k][s] == 'W':
                        cnt2 += 1
                elif k % 2 == 0 and s % 2 == 1:
                    if m_list[k][s] == 'B':
                        cnt2 += 1
                elif k % 2 == 1 and s % 2 == 0:
                    if m_list[k][s] == 'B':
                        cnt2 += 1
        n_min = min(n_min, cnt1, cnt2)
print(n_min)