121차 1번 문제풀이(푸는중)

Author: gmlrude

live12/test121/문제1/박희경.py

@@ -0,0 +1,32 @@
+import sys
+
+input = sys.stdin.readline
+
+n, m, k = map(int, input().split())
+board = []
+for _ in range(n):
+    board.append(list(map(str, input().rstrip())))
+
+prefix_sum_black = [[0] * (m + 1) for _ in range(n + 1)]
+prefix_sum_white = [[0] * (m + 1) for _ in range(n + 1)]
+
+for i in range(n):
+    for j in range(m):
+        prefix_sum_black[i][j] = prefix_sum_black[i-1][j] + prefix_sum_black[i][j-1] - prefix_sum_black[i-1][j-1]
+        prefix_sum_white[i][j] = prefix_sum_white[i-1][j] + prefix_sum_white[i][j-1] - prefix_sum_white[i-1][j-1] 
+        if (i + j) % 2 == 0:
+            if board[i][j] != 'B':
+                # 바꿔야 함
+                prefix_sum_black[i][j] += 1
+        else:
+            if board[i][j] == 'B':
+                prefix_sum_white[i][j] += 1
+
+count = float('inf')
+for i in range(1, n - k + 2):
+    for j in range(1, m  - k + 2):
+        black_cnt = prefix_sum_black[i + k - 1][j + k - 1] - prefix_sum_black[i + k - 1][j - 1] - prefix_sum_black[i - 1][j + k - 1] + prefix_sum_black[i - 1][j - 1]
+        white_cnt = prefix_sum_white[i + k - 1][j + k - 1] - prefix_sum_white[i + k - 1][j - 1] - prefix_sum_white[i - 1][j + k - 1] + prefix_sum_white[i - 1][j - 1]
+        count = min(count, black_cnt, white_cnt)
+
+print(count)