7569 토마토 (JAVA)

• 3차원인 점만 고려한다면, 전형적인 BFS 문제이다.
• 3차원 배열의 입력과 dz 배열을 유념하여 푼다.

import java.util.*;
public class Main {

    static class Point{
        int hei;
        int wid;
        int z;
        public Point(int z ,int hei, int wid) {
            this.z = z;
            this.hei = hei;
            this.wid = wid;
        }
    }

    static int w,h,z;
    static int[][][] graph;
    static boolean[][][] ch;
    
    // dz 배열의 추가.
    static int[] dx = {-1,0,0,1,0,0};
    static int[] dy = {0,1,-1,0,0,0};
    static int[] dz = {0,0,0,0,-1,1};
    static ArrayList<Point> init;
    static int bfs(){
        int L = 0;
        Queue<Point> q = new LinkedList<>();
        for(Point p : init) {
            ch[p.z][p.hei][p.wid] = true;
            q.offer(p);
        }
        while(!q.isEmpty()){
            int len = q.size();
            for(int i=0; i<len; ++i){
                Point v = q.poll();
                for(int j=0; j<dx.length; ++j){
                    int vhei = v.hei + dy[j];
                    int vwid = v.wid + dx[j];
                    int vz = v.z + dz[j];
                    if(vhei >= 0 && vwid >= 0 && vz >= 0
                    && vhei < h && vwid < w && vz < z
                    && !ch[vz][vhei][vwid] && graph[vz][vhei][vwid]==0){
                        ch[vz][vhei][vwid] = true;
                        graph[vz][vhei][vwid] = 1;
                        q.offer(new Point(vz, vhei, vwid));
                    }
                }
            }
            L++;
        }
        return L;
    }

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        w = sc.nextInt();
        h = sc.nextInt();
        z = sc.nextInt();
        graph = new int[z][h][w];
        ch = new boolean[z][h][w];
        for(int k = 0; k < z; ++k)
            for (int i = 0; i < h; ++i)
               for (int j = 0; j < w; ++j)
                    graph[k][i][j] = sc.nextInt();

        init = new ArrayList<>();

        for(int k = 0; k < z; ++k)
            for (int i = 0; i < h; ++i) {
                for (int j = 0; j < w; ++j) {
                    if(graph[k][i][j] == 1)
                        init.add(new Point(k,i,j));
                }
            }

        int answer = bfs()-1;
        boolean done = true;
        for(int k = 0; k < z; ++k)
            for (int i = 0; i < h; ++i) {
                for (int j = 0; j < w; ++j) {
                    if(graph[k][i][j] == 0)
                        done = false;
                }
            }

        if(done)
            System.out.println(answer);
        else
            System.out.println(-1);
    }
}