Merge pull request #197 from sds-2021-summer-algorithm/yukyeongmin-pa…

…tch-3

[유경민] 빙산

solution/BOJ_2573_빙산/ykm.java

@@ -0,0 +1,123 @@
+import java.io.BufferedReader;
+import java.io.FileInputStream;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.util.StringTokenizer;
+
+public class Main {
+    static int N; // 행
+    static int M; // 열
+    static int[][][] Map; // 위치, 빙산의 높이정보, 턴 정보
+    static boolean[][] isVisited;
+    static int ice = 0; // 빙산이 차지하고 있는 넓이 -> 빙산이 줄어드는지 확인할때 사용할 예정
+
+    static int[] mx = { -1, 1, 0, 0 };
+    static int[] my = { 0, 0, -1, 1 };
+
+    public static void main(String[] args) throws IOException {
+        System.setIn(new FileInputStream("input.txt"));
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+
+        StringTokenizer st = new StringTokenizer(br.readLine());
+        N = Integer.parseInt(st.nextToken());
+        M = Integer.parseInt(st.nextToken());
+
+        Map = new int[N][M][2];
+
+        for (int i = 0; i < N; i++) {
+            st = new StringTokenizer(br.readLine());
+            for (int j = 0; j < M; j++) {
+                Map[i][j][0] = Integer.parseInt(st.nextToken());
+                if (Map[i][j][0] > 0)
+                    ice++;
+            }
+        }
+
+        int turn = 1;
+        while (true) {
+            for (int i = 0; i < N; i++) {
+                for (int j = 0; j < M; j++) {
+                    if (Map[i][j][0] > 0) {
+                        melt(i, j, turn);
+                    }
+                }
+            }
+            int c = check();
+            if (c == -1) {
+                System.out.println(0);
+                break;
+            } else if (c < ice) {
+                System.out.println(turn);
+                break;
+            }
+            turn++;
+
+        }
+        br.close();
+    }
+
+    private static void melt(int x, int y, int turn) {
+
+        for (int i = 0; i < 4; i++) {
+            int nextX = x + mx[i];
+            int nextY = y + my[i];
+
+            if (nextX < 0 || nextY < 0 || nextX >= N || nextY >= M)
+                continue;
+
+            // 주위에 0이 있으면 녹음
+            // 갓 녹은 빙하 주의
+            if (Map[nextX][nextY][0] == 0 && Map[nextX][nextY][1] < turn) {
+                Map[x][y][0]--;
+
+                // 모두 녹으면
+                if (Map[x][y][0] == 0) {
+                    Map[x][y][1] = turn;
+                    ice--;
+                    break;
+                }
+            }
+        }
+    }
+
+    // 빙산의 일부를 찾아 이어진 모든 빙산의 넓이를 구하기
+    // dfs
+    private static int check() {
+        for (int i = 0; i < N; i++) {
+            for (int j = 0; j < M; j++) {
+
+                if (Map[i][j][0] == 0)
+                    continue;
+                else {
+                    isVisited = new boolean[N][M];
+                    isVisited[i][j] = true;
+                    return dfs(i, j, 1);
+                }
+            }
+        }
+
+        // 모두 녹은 상태
+        return -1;
+    }
+
+    private static int dfs(int x, int y, int area) {
+
+        for (int i = 0; i < 4; i++) {
+            int nextX = x + mx[i];
+            int nextY = y + my[i];
+
+            if (nextX < 0 || nextY < 0 || nextX >= N || nextY >= M)
+                continue;
+            if (isVisited[nextX][nextY])
+                continue;
+            if (Map[nextX][nextY][0] == 0)
+                continue;
+            else {
+                isVisited[nextX][nextY] = true;
+                area = dfs(nextX, nextY, area + 1);
+            }
+        }
+
+        return area;
+    }
+}