[BOJ] 15683 감시 (G3)

Author: poodlepoodle

최어진/7주차/260214.py

@@ -0,0 +1,119 @@
+# 백준 15683번: 감시 (2회차)
+
+import sys
+
+input = sys.stdin.readline
+
+# N, M <= 8
+N, M = map(int, input().rstrip().split())
+maps = [list(map(int, input().rstrip().split())) for _ in range(N)]
+watchs = [[0 for _ in range(M)] for _ in range(N)]
+
+# 0은 빈 칸
+# 1~5는 CCTV (<= 8개)
+# 6은 벽
+EMTPY = 0
+WALL = 6
+
+cctvs = []
+emptys = 0
+for r in range(N):
+    for c in range(M):
+        if maps[r][c] == EMTPY:
+            emptys += 1
+        elif maps[r][c] < WALL:
+            cctvs.append((maps[r][c], r, c))
+# for row in maps:
+#     print(row)
+# print()
+
+# 브루트포싱:
+# 1. 8개의 CCTV가 4개 방향 = 4^8 = 2^16 <= 10^5
+# 2. 각 CCTV 방향마다 8개 칸
+# 10^6 안쪽으로 통과할 것으로 기대
+ 
+directions_per_cctv_types = {
+    1: [
+        [0],
+        [1],
+        [2],
+        [3]
+    ],
+    2: [
+        [0, 2],
+        [1, 3]
+    ],
+    3: [
+        [0, 1],
+        [1, 2],
+        [2, 3],
+        [3, 0]
+    ],
+    4: [
+        [0, 1, 2],
+        [1, 2, 3],
+        [2, 3, 0],
+        [3, 0, 1]
+    ],
+    5: [
+        [0, 1, 2, 3]
+    ],
+}
+moves = [
+    [-1, 0],
+    [0, 1],
+    [1, 0],
+    [0, -1]
+]
+
+def is_valid_position(r, c):
+    return 0 <= r < N and 0 <= c < M
+
+def print_maps():
+    for r in range(N):
+        for c in range(M):
+            if watchs[r][c] > 0: print('*', end='')
+            elif maps[r][c] == WALL: print('#', end='')
+            elif maps[r][c] == EMTPY: print('.', end='')
+            else: print(maps[r][c], end='')
+        print()
+    print()
+
+def bruteforcing(idx):
+    # print(f'bruteforcing({idx})')
+    global emptys, answer
+    
+    if idx >= len(cctvs):
+        # print(f'---- searched: {emptys} ----')
+        # print_maps()
+        answer = min(answer, emptys)
+        return
+    
+    cctv_type, cctv_r, cctv_c = cctvs[idx]
+    for views in directions_per_cctv_types[cctv_type]:
+        # print('views:', views)
+        # 각 시야각 별 감시 시작
+        for direction in views:
+            # print('direction:', direction)
+            r, c = cctv_r, cctv_c
+            dr, dc = moves[direction]
+            while is_valid_position(r + dr, c + dc) and maps[r + dr][c + dc] < WALL:
+                r, c = r + dr, c + dc
+                if not watchs[r][c] and maps[r][c] == EMTPY:
+                    emptys -= 1
+                watchs[r][c] += 1
+        # 다음 CCTV 브루트포싱
+        bruteforcing(idx + 1)
+        # 감시 해제
+        for direction in views:
+            r, c = cctv_r, cctv_c
+            dr, dc = moves[direction]
+            while is_valid_position(r + dr, c + dc) and maps[r + dr][c + dc] < WALL:
+                r, c = r + dr, c + dc
+                watchs[r][c] -= 1
+                if not watchs[r][c] and maps[r][c] == EMTPY:
+                    emptys += 1
+    
+answer = int(1e9)
+bruteforcing(0)
+print(answer)