[20251015] BOJ / G3 / 치즈 / 이종환

0224LJH/202510/15 BOJ 치즈.md

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+```java
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.util.*;
+import java.awt.Point;
+
+public class Main {
+
+	static int height, width, round,ans;
+	static int[][] arr;
+	static Queue<Point> cheeses = new LinkedList<>();
+
+	static int[] dy = { -1,0,1,0};
+	static int[] dx = { 0,1,0,-1};
+
+	static final int OUTSIDE = 0;
+	static final int CHEESE = 1;
+	static final int INSIDE = 2;
+
+
+    public static void main(String[] args) throws NumberFormatException, IOException {
+    	init();
+    	process();
+    	print();
+    }
+
+
+
+    public static void init() throws NumberFormatException, IOException {
+    	BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+    	StringTokenizer st = new StringTokenizer(br.readLine());
+    	height = Integer.parseInt(st.nextToken());
+    	width = Integer.parseInt(st.nextToken());
+    	arr = new int[height][width];
+
+    	for (int i = 0; i < height; i++) {
+    		st = new StringTokenizer(br.readLine());
+    		for (int j = 0; j < width; j++) {
+    			arr[i][j] = Integer.parseInt(st.nextToken());
+    		}
+    	}
+
+	}
+
+    public static void process() throws IOException { 	
+
+    	findInside();
+    	int second = 0;
+    	while (!cheeses.isEmpty()) {
+    		melt();
+    		second++;
+    	}
+
+
+    	ans = second;
+    }
+
+    private static void melt() {
+    	Queue<Point> cheeseLeft = new LinkedList<>();
+    	Queue<Point> deleteQ = new LinkedList<>();
+
+    	while(!cheeses.isEmpty()) {
+    		Point p = cheeses.poll();
+
+    		if(isNotMelting(p.y , p.x)) {
+    			cheeseLeft.add(p);
+    			continue;
+    		}
+    		deleteQ.add(p);
+    	}
+
+    	while(!deleteQ.isEmpty()) {
+    		Point p = deleteQ.poll();
+
+    		arr[p.y][p.x] = OUTSIDE;
+
+    		for (int i = 0; i <4 ; i++) {
+    			int ny = p.y + dy[i];
+    			int nx = p.x + dx[i];
+    			if ( ny < 0 || nx < 0 || ny >= height || nx >= width 
+    					|| arr[ny][nx] == CHEESE || arr[ny][nx] == OUTSIDE) continue;
+
+    			arr[ny][nx] = OUTSIDE;
+    			Point nPoint = new Point(nx,ny); 
+
+    			Queue<Point> insideCheese = new LinkedList<>();
+
+    			insideCheese.add(nPoint);
+    			while(!insideCheese.isEmpty()) {
+    				Point iP =insideCheese.poll();
+    				for (int j = 0; j < 4; j++) {
+    					int nIy = iP.y + dy[j];
+    					int nIx = iP.x + dx[j];
+    					if ( nIy < 0 || nIx < 0 || nIy >= height || nIx >= width 
+    	    					|| arr[nIy][nIx] == CHEESE || arr[nIy][nIx] == OUTSIDE) continue;
+
+    					arr[nIy][nIx] = OUTSIDE;
+    					insideCheese.add(new Point(nIx, nIy));
+    				}
+    			}
+    		}
+    	}
+
+    	cheeses = cheeseLeft;
+
+
+    }
+    private static boolean isNotMelting(int y,int x) {
+
+    	int outSideCnt = 0;
+
+    	for (int i = 0 ; i < 4; i++) {
+			int ny = y + dy[i];
+			int nx = x + dx[i];
+			if ( ny < 0 || nx < 0 || ny >= height || nx >= width || arr[ny][nx] == OUTSIDE) outSideCnt++;
+    	}
+//    	System.out.println(y  + " " + x + " -> "+ outSideCnt);
+
+    	return (outSideCnt < 2) ;
+    }
+
+    private static void findInside() {
+    	boolean[][] visited = new boolean[height][width];
+
+    	for (int i = 0; i < height; i++) {
+    		for (int j = 0; j < width; j++) {
+    			if (visited[i][j] ) continue;
+    			if (arr[i][j] == CHEESE) {
+    				cheeses.add(new Point(j,i));
+    				continue;
+    			}
+
+    			Queue<Point> q = new LinkedList<>();
+    			Set<Point> set = new HashSet<>();
+
+    			Point start = new Point(j,i);
+    			boolean isInside = true;
+    			q.add(start);
+    			set.add(start);
+
+    			while(!q.isEmpty()) {
+    				Point p = q.poll();
+
+    				for (int k = 0; k <4 ; k++) {
+    					int ny = p.y + dy[k];
+    					int nx = p.x + dx[k];
+
+    					if ( ny < 0 || nx < 0 || ny >= height || nx >= width) {
+    						// 밖으로 벗어남 -> 치즈안이 아님
+    						isInside = false;
+    						continue;
+    					}
+
+    					if (visited[ny][nx] || arr[ny][nx] == CHEESE) continue;
+
+    					Point np = new Point(nx, ny);
+    					q.add(np);
+    					set.add(np);
+    					visited[ny][nx] = true;
+
+    				}
+    			}
+
+    			for (Point p:set) {
+    				arr[p.y][p.x] = (isInside)?2:0; 
+    			}
+
+    		}
+    	}
+    }
+
+
+
+
+	public static void print() {
+		System.out.println(ans);
+
+    }
+}
+```