[황정훈] 빙산

solution/BOJ_2573_빙산/황정훈.java

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+import java.io.*;
+import java.util.*;
+
+public class Main {
+
+    static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+    static BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
+    static StringTokenizer st;
+
+    static int N, M, Y = 0, mass = 1;
+    static int[] dr = {-1, 0, 1, 0};
+    static int[] dc = {0, 1, 0, -1};
+    static int[][] map;
+    static class Point{
+        int r, c;
+        public Point(int r, int c){
+            this.r = r;
+            this.c = c;
+        }
+    }
+    static boolean[][] visit;
+    static Queue<Point> Q;
+
+    public static void main(String[] args) throws Exception {
+
+        st = new StringTokenizer(br.readLine());
+        N = Integer.parseInt(st.nextToken());
+        M = Integer.parseInt(st.nextToken());
+        map = new int[N][M];
+        for (int i = 0; i < N; i++) {
+            st = new StringTokenizer(br.readLine());
+            for (int j = 0; j < M; j++) {
+                map[i][j] = Integer.parseInt(st.nextToken());
+            }
+        }
+
+        while(mass==1){
+            Y++;
+            melt();
+            split_check();
+        }
+
+        bw.write(mass>1 ? Y+"\n" : "0\n");
+        bw.flush();
+        bw.close();
+        br.close();
+    }
+    static void melt(){
+        int[][] tmp = new int[N][M];
+        for (int i = 1; i < N-1; i++) {
+            for (int j = 1; j < M-1; j++) {
+                if (map[i][j]<=0) continue;
+                int cnt = 0;
+                for (int w = 0; w < 4; w++) {
+                    int nr = i + dr[w];
+                    int nc = j + dc[w];
+                    if(map[nr][nc]<=0) cnt++;
+                }
+                tmp[i][j] -= cnt;
+            }
+        }
+
+        for (int i = 1; i < N-1; i++) {
+            for (int j = 1; j < M-1; j++) {
+                map[i][j] += tmp[i][j];
+            }
+        }
+    }
+    static void split_check(){
+        mass = 0;
+        visit = new boolean[N][M];
+
+        for (int i = 1; i < N-1; i++) {
+            for (int j = 1; j < M-1; j++) {
+                if (map[i][j]>0 && !visit[i][j]){
+                    mass++;
+                    bfs(i, j);
+                }
+            }
+        }
+    }
+    static void bfs(int i, int j){
+        Q = new ArrayDeque<>();
+        Q.add(new Point(i, j));
+        visit[i][j] = true;
+
+        while(!Q.isEmpty()){
+            Point cur = Q.poll();
+            for (int w = 0; w < 4; w++) {
+                int nr = cur.r + dr[w];
+                int nc = cur.c + dc[w];
+                if (map[nr][nc]>0 && !visit[nr][nc]){
+                    Q.add(new Point(nr, nc));
+                    visit[nr][nc] = true;
+                }
+            }
+        }
+    }
+}