[BOJ] 17142 연구소 3 (G3)

Author: poodlepoodle

최어진/8주차/260219.py

@@ -0,0 +1,87 @@
+# 백준 17142번: 연구소 3 (3회차)
+
+from collections import deque
+from itertools import combinations
+import sys
+
+input = sys.stdin.readline
+
+# N <= 50
+# M <= 10
+N, M = map(int, input().rstrip().split())
+maps = [list(map(int, input().rstrip().split())) for _ in range(N)]
+
+EMPTY = 0
+WALL = 1
+VIRUS = 2
+NOT_VISITED = -1
+
+total_viruses = []
+for r in range(N):
+    for c in range(N):
+        if maps[r][c] == VIRUS: total_viruses.append((r, c))
+
+# 바이러스 조합
+#   10개 중 M개 선택 -> 10CM <= 10C5 = 252 < 10^3
+# 각 조합마다 바이러스 퍼지는 시뮬레이션
+#   모든 칸에 대한 BFS -> O(N^2) = 2500 < 10^4
+# 결론: 10^3 * 10^4 < 10^8
+
+moves = [
+    [0, 1],
+    [0, -1],
+    [1, 0],
+    [-1, 0],
+]
+
+def is_in_board(r, c):
+    return 0 <= r < N and 0 <= c < N
+
+def print_visited(visited):
+    print('#-------#')
+    for r in range(N):
+        for c in range(N):
+            if maps[r][c] == WALL: print('-', end=' ')
+            elif visited[r][c] == NOT_VISITED:
+                if maps[r][c] == VIRUS: print('*', end=' ')
+                else: print('-', end=' ')
+            else: print(visited[r][c], end=' ')
+        print()
+    print('#-------#')
+    print()
+
+def bfs(viruses):
+    q = deque()
+    visited = [[-1 for _ in range(N)] for _ in range(N)]
+    moved_max = 0
+
+    for vr, vc in viruses:
+        q.append((vr, vc, 0))
+        visited[vr][vc] = 0
+
+    while q:
+        r, c, moved = q.popleft()
+        if maps[r][c] == EMPTY:
+            moved_max = max(moved_max, moved)
+
+        for dr, dc in moves:
+            if is_in_board(r + dr, c + dc):
+                if maps[r + dr][c + dc] != WALL and visited[r + dr][c + dc] == NOT_VISITED:
+                    q.append((r + dr, c + dc, moved + 1))
+                    visited[r + dr][c + dc] = moved + 1
+    
+    # print_visited(visited)
+
+    for r in range(N):
+        for c in range(N):
+            if maps[r][c] == EMPTY and visited[r][c] == NOT_VISITED: return -1
+    
+    return moved_max
+
+answer = int(1e9)
+for viruses in combinations(total_viruses, M):
+    current_answer = bfs(viruses)
+    if current_answer != -1:
+        answer = min(answer, current_answer)
+
+print(answer if answer != int(1e9) else -1)