[BOJ]14502_연구소/ Gold / 60min

https://www.acmicpc.net/problem/14502

Author: zaqquum

Hongjoo/백준/연구소.py

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+
+
+"""
+
+(1) 벽 3개 - 세우기 ->  0중 3 개 조합 구하기
+(2) BFS -> 확산시키기 
+(3) 안전 영역 계산하기  -> min 이란 비교시 업데이트 
+(4) 조합 replay
+
+#bfs 
+visited = [False] * 9
+def bfs(graph, start, visited):
+# start -> queue, visited 
+    queue = deque([start])
+    visited[start] = True
+    while queue : 
+        node= queue.popleft()
+        for i in  graph[node]:
+            if not visited[i]:
+                queue.append(i)
+                visited[i] = True
+
+
+"""
+from itertools import combinations
+from collections import deque
+import sys
+import copy
+
+a,b= map(int, sys.stdin.readline().split()) # row, columns
+
+m = []
+zero_p = []
+virus_p = []
+for i in range(a):
+    tmp = list(map(int, input().split()))
+    for j  in range(b) :
+        if tmp[j] == 0:
+            zero_p.append([i,j])
+        elif tmp[j] == 2 :
+            virus_p.append([i,j])
+    m.append(tmp)
+# print(m)
+#1. zero_p 중 3개 조합 구하기 -> combi
+combi = list(combinations(zero_p , 3))
+
+#2. BFS
+max_safe= 0
+for walls in combi:
+    graph=copy.deepcopy(m)
+    # 벽설치
+    for w_x, w_y in walls : 
+        graph[w_x][w_y]  = 1 
+    
+    new_v_count =0
+    # virus 들위 위치 = BFS start 위치
+    for v in range(len(virus_p)) :
+        start=virus_p[v] # start = [x,y]
+        queue = deque([start])
+        #bfs
+        while queue :
+            node = queue.popleft()
+            # print("#",node, end ="")
+            # 인근 node - 상/하/좌/우
+            near_node = [[node[0]+1,node[1]] ,
+                          [node[0]-1,node[1]],
+                           [node[0],node[1]+1],
+                            [node[0],node[1]-1] ]
+            
+            for nn in near_node : 
+                x,y = nn
+                # out of range 
+                if x < 0 or  x >= a or y <0 or y>=b :
+                    # print("bump!")
+                    continue
+                # print(x,y)
+                if graph[x][y] == 0 : #방문 x 
+                    queue.append(nn)
+                    graph[x][y] = 2 # 방문 완료
+                    new_v_count+= 1
+    
+        
+    #(3) 안전 영역 계산하기  -> min 이란 비교시 업데이트
+    safe_area = len(zero_p)-3 -new_v_count
+    if max_safe < safe_area :
+        max_safe = safe_area
+print(f"{max_safe}")
+
+