[BOJ] 백준 2573 빙산

[문제]

https://www.acmicpc.net/problem/2573

 

 

[소스 코드]

import java.io.*;
import java.util.*;

public class Main {
	static int n,m;
	static int[][] map;
	static int[] dr = {-1,1,0,0};
	static int[] dc = {0,0,-1,1};
	public static void main(String[] args) throws IOException {
		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];
		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());
			}
		}
		int year = 0;
		while(true) {
			melt();
			year++;
			int result = count();
			if(result>1) {
				System.out.println(year);
				break;
			}
			if(result==0) {
				System.out.println(0);
				break;
			}
		}
	}
	private static void melt() {
		int[][] add = new int[n][m];
		for(int i=0;i<n;i++) {
			for(int j=0;j<m;j++) {
				if(map[i][j]>0) {
					for(int d=0;d<4;d++) {
						int nr = i + dr[d];
						int nc = j + dc[d];
						if(nr<0 || nr>=n || nc<0 || nc>=m) continue;
						if(map[nr][nc]==0) {
							add[i][j]++;
						}
					}
				}
			}
		}
		for(int i=0;i<n;i++) {
			for(int j=0;j<m;j++) {
				if(map[i][j]<=add[i][j]) map[i][j] = 0;
				else map[i][j] -= add[i][j];
			}
		}
	}
	private static int count() {
		int cnt = 0;
		boolean[][] visit = new boolean[n][m];
		Queue<int[]> q = new LinkedList<>();
		for(int i=0;i<n;i++) {
			for(int j=0;j<m;j++) {
				if(map[i][j]>0 && !visit[i][j]) {
					visit[i][j] = true;
					q.offer(new int[] {i,j});
					cnt++;
					while(!q.isEmpty()) {
						int[] curr = q.poll();
						for(int d=0;d<4;d++) {
							int nr = curr[0] + dr[d];
							int nc = curr[1] + dc[d];
							if(nr<0 || nr>=n || nc<0 || nc>=m || visit[nr][nc]) continue;
							if(map[nr][nc]>0) {
								visit[nr][nc] = true;
								q.offer(new int[] {nr,nc});
							}
						}
					}
				}
			}
		}
		return cnt;
	}
}