From 01fbdd4ab3c182b3b969e3a9e046ca0f3a6cdca7 Mon Sep 17 00:00:00 2001
From: JSPark <48265129+pknujsp@users.noreply.github.com>
Date: Fri, 29 Mar 2024 16:54:00 +0900
Subject: [PATCH] 2024-03-29

---
 ...4 \353\247\214\353\223\244\352\270\260.py" | 76 +++++++++++++++++++
 pknujsp/README.md                             |  3 +-
 2 files changed, 78 insertions(+), 1 deletion(-)
 create mode 100644 "pknujsp/BFS/42-\353\213\244\353\246\254 \353\247\214\353\223\244\352\270\260.py"

diff --git "a/pknujsp/BFS/42-\353\213\244\353\246\254 \353\247\214\353\223\244\352\270\260.py" "b/pknujsp/BFS/42-\353\213\244\353\246\254 \353\247\214\353\223\244\352\270\260.py"
new file mode 100644
index 00000000..a36ea91b
--- /dev/null
+++ "b/pknujsp/BFS/42-\353\213\244\353\246\254 \353\247\214\353\223\244\352\270\260.py"	
@@ -0,0 +1,76 @@
+from collections import *
+
+map_size = int(input())
+matrix = [list(map(int, input().split())) for _ in range(map_size)]
+
+directions = [(1, 0), (0, -1), (-1, 0), (0, 1)]
+island_id = 2
+costs = [[0] * map_size for _ in range(map_size)]
+
+# 다리를 놓을 위치를 저장할 큐
+bridge_queue = deque()
+
+# 전체 맵을 순회하면서 각 섬에 ID 부여
+for row in range(map_size):
+    for col in range(map_size):
+        
+        if matrix[row][col] != 1:
+            continue
+            
+        # 현재 칸을 시작으로 하는 섬에 고유 ID 할당
+        matrix[row][col] = island_id
+        queue = deque([(row, col)])
+        
+        # BFS를 통해 같은 섬인 육지에 ID 할당
+        while queue:
+            r, c = queue.popleft()
+            # 육지 영역은 다리 영역 탐색 시에 제외함
+            costs[r][c] = -1
+            
+            for dr, dc in directions:
+                nr, nc = r + dr, c + dc
+
+                if not 0 <= nr < map_size or not 0 <= nc < map_size:
+                    continue
+                    
+                # 다른 섬과 연결된 바다 영역에 접근하면 종료
+                if 1 < matrix[nr][nc] < island_id:
+                    print(1)
+                    exit()
+                    
+                # 새로운 육지 발견 시 큐에 추가
+                if matrix[nr][nc] == 1:
+                    queue.append((nr, nc))
+                # 육지와 바로 맞닿은 바다 영역을 다리 후보로 추가
+                elif matrix[nr][nc] == costs[nr][nc] == 0:
+                    bridge_queue.append((nr, nc, 1, island_id))
+                    
+                costs[nr][nc] = 1
+                matrix[nr][nc] = island_id
+                
+        island_id += 1
+
+min_cost = int(1e6)
+
+# 다리 후보 위치를 순회하며 최소 다리 길이 계산
+while bridge_queue:
+    r, c, cost, curr_island_id = bridge_queue.popleft()
+    
+    for dr, dc in directions:
+        nr, nc = r + dr, c + dc
+        
+        if not 0 <= nr < map_size or not 0 <= nc < map_size:
+            continue
+            
+        # 아직 다리가 놓이지 않은 바다 영역이면
+        # 다리 길이를 증가시키고 큐에 추가
+        if costs[nr][nc] == 0:
+            bridge_queue.append((nr, nc, cost + 1, curr_island_id))
+            
+            costs[nr][nc] = cost + 1
+            matrix[nr][nc] = curr_island_id
+        # 다른 섬과 연결된 다리 영역에 접근하였다면 최소 비용을 갱신
+        elif matrix[nr][nc] > 1 and matrix[nr][nc] != curr_island_id:
+            min_cost = min(min_cost, cost + costs[nr][nc])
+
+print(min_cost)
diff --git a/pknujsp/README.md b/pknujsp/README.md
index 665f42d8..078a8f94 100644
--- a/pknujsp/README.md
+++ b/pknujsp/README.md
@@ -42,4 +42,5 @@
 | 38차시 | 2024.03.08 |   BRUTE_FORCE   |         [자물쇠와 열쇠](https://school.programmers.co.kr/learn/courses/30/lessons/60059)          | [#154](https://github.com/AlgoLeadMe/AlgoLeadMe-1/pull/154) |
 | 39차시 | 2024.03.19 |       큐        |        [디스크 컨트롤러](https://school.programmers.co.kr/learn/courses/30/lessons/42627)         | [#163](https://github.com/AlgoLeadMe/AlgoLeadMe-1/pull/163) |
 | 40차시 | 2024.03.22 |     그리디      |                           [센서](https://www.acmicpc.net/problem/2212)                            | [#168](https://github.com/AlgoLeadMe/AlgoLeadMe-1/pull/168) |
-| 41차시 | 2024.03.25 |   다익스트라    |                         [알고스팟](https://www.acmicpc.net/problem/1261)                          | [#169](https://github.com/AlgoLeadMe/AlgoLeadMe-1/pull/169) |
\ No newline at end of file
+| 41차시 | 2024.03.25 |   다익스트라    |                         [알고스팟](https://www.acmicpc.net/problem/1261)                          | [#169](https://github.com/AlgoLeadMe/AlgoLeadMe-1/pull/169) |
+| 42차시 | 2024.03.29 |       BFS       |                        [다리 만들기](https://www.acmicpc.net/problem/2146)                        | [#173](https://github.com/AlgoLeadMe/AlgoLeadMe-1/pull/173) |
\ No newline at end of file