30-kangrae-jo

kangrae-jo/Queue/30-kangrae-jo.cpp

@@ -0,0 +1,90 @@
+#include <iostream>
+#include <queue>
+#include <vector>
+
+using namespace std;
+
+const int AIR = -1;
+const int EMPTY = 0;
+const int CHEESE = 1;
+const int OFFSET[4][2] = {{1, 0}, {0, 1}, {-1, 0}, {0, -1}};
+
+int N, M;
+vector<vector<int>> board;
+
+bool isIn(int y, int x) { return 0 <= y && y < N && 0 <= x && x < M; }
+
+void markAir() {
+    vector<vector<bool>> visited(N, vector<bool>(M, false));
+    queue<pair<int, int>> q;
+    q.push({0, 0});
+    visited[0][0] = true;
+    board[0][0] = AIR;
+
+    while (!q.empty()) {
+        auto [y, x] = q.front();
+        q.pop();
+
+        for (int dir = 0; dir < 4; dir++) {
+            int y_ = y + OFFSET[dir][0];
+            int x_ = x + OFFSET[dir][1];
+            if (isIn(y_, x_) && !visited[y_][x_] && board[y_][x_] == EMPTY) {
+                visited[y_][x_] = true;
+                board[y_][x_] = AIR;
+                q.push({y_, x_});
+            }
+        }
+    }
+}
+
+bool melt() {
+    vector<pair<int, int>> cheeseToMelt;
+    for (int y = 0; y < N; y++) {
+        for (int x = 0; x < M; x++) {
+            if (board[y][x] == CHEESE) {
+                int contact = 0;
+                for (int dir = 0; dir < 4; dir++) {
+                    int y_ = y + OFFSET[dir][0];
+                    int x_ = x + OFFSET[dir][1];
+                    if (isIn(y_, x_) && board[y_][x_] == AIR) contact++;
+                }
+                if (contact >= 2) cheeseToMelt.push_back({y, x});
+            }
+        }
+    }
+    for (auto [y, x] : cheeseToMelt) board[y][x] = EMPTY;
+
+    return !cheeseToMelt.empty();
+}
+
+void resetAir() {
+    for (int y = 0; y < N; y++) {
+        for (int x = 0; x < M; x++) {
+            if (board[y][x] == AIR) board[y][x] = EMPTY;
+        }
+    }
+}
+
+int main() {
+    ios_base::sync_with_stdio(0);
+    cout.tie(0);
+    cin.tie(0);
+
+    cin >> N >> M;
+    board.assign(N, vector<int>(M));
+    for (int y = 0; y < N; y++) {
+        for (int x = 0; x < M; x++) {
+            cin >> board[y][x];
+        }
+    }
+
+    int answer = 0;
+    while (++answer) {
+        markAir();           // 바깥 공기 == AIR
+        if (!melt()) break;  // 녹일 치즈 없으면 종료
+        resetAir();          // AIR = EMPTY 복구 
+    }
+    cout << answer - 1;
+
+    return 0;
+}

kangrae-jo/README.md

@@ -31,3 +31,4 @@
 | 27차시 | 2024.06.01 |  DFS  | [개미굴](https://www.acmicpc.net/problem/14725)|[#107](https://github.com/AlgoLeadMe/AlgoLeadMe-12/pull/107)|
 | 28차시 | 2024.06.10 |  BFS  | [경주로 건설](https://school.programmers.co.kr/learn/courses/30/lessons/67259)|[#110](https://github.com/AlgoLeadMe/AlgoLeadMe-12/pull/110)|
 | 29차시 | 2024.06.19 |  TRIE  | [[3차] 자동완성](https://school.programmers.co.kr/learn/courses/30/lessons/17685)|[#114](https://github.com/AlgoLeadMe/AlgoLeadMe-12/pull/114)|
+| 30차시 | 2024.07.18 |  BFS  | [치즈](https://www.acmicpc.net/problem/2638)|[#117](https://github.com/AlgoLeadMe/AlgoLeadMe-12/pull/117)|