[Java] 너비우선탐색 (BFS) 미로찾기 Queue구현

너비우선탐색(BFS) 최대한 넓게 이동한 후 더 이상 갈 수 없을 경우 아래로 이동한다.

인접한 노드를 먼저 탐색하고, 가장 멀리 떨어져 있는 정점을 가장 나중에 방문한다.

 

최단 경로를 찾고자 할 경우 주로 사용한다.

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1. map : 갈 수 있는 길은 0, 갈 수 없는 길은 1이다.

 

2. enqueue한 길도 벽으로 변경하여 여러번 enqueue할 수 없도록 한다. (방문 처리)

 

3. class Index : Queue에 담을 객체 ( x와 y의 좌표를 가지고 있다.)

 

4. 현재 인덱스를 저장하고 있는 Index 클래스를 매개변수로 받아

     findWay() 메서드에서 상하좌우를 탐색하고 enqueue한다.

 

5. enqueue한 Index를 dequeue해 위치를 이동한다. <- while 반복 : 종료 위치에 도착할 때 까지.

 

import java.util.LinkedList;
import java.util.Queue;

public class BfsQueue {
	public static void main(String[] args) {
		// 7(골인)을 찾을때 까지 너비우선탐색
		bfs(0,0);
	}
	
	//지도
	public static int[][] map = 
			{{0,1,1,1,1,0,0,0,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1},
			{0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
			{0,1,1,1,1,0,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,0},
			{0,1,0,0,0,0,0,0,0,0,0,0,1,0,1,1,0,1,0,1,0,0,0,0},
			{0,1,0,1,0,1,1,1,1,1,1,0,1,0,0,1,0,1,0,1,0,1,1,1},
			{0,1,0,1,0,1,0,0,0,0,1,0,1,1,0,1,0,1,0,1,0,0,0,0},
			{0,1,0,1,0,1,1,1,1,0,1,0,0,0,0,1,0,1,0,1,1,1,1,0},
			{0,0,0,1,0,0,0,0,0,0,1,1,1,1,0,1,0,1,0,0,0,0,0,0},
			{0,1,1,1,1,0,1,0,1,0,1,1,1,1,0,1,0,1,1,1,0,1,0,1},
			{0,0,0,0,1,1,1,0,1,0,1,0,0,0,0,1,0,0,0,0,0,1,0,0},
			{1,0,1,0,1,0,0,0,1,0,1,0,1,1,0,1,1,1,1,1,1,1,1,1},
			{0,0,1,0,1,0,1,0,1,0,1,0,1,0,0,0,0,0,1,0,0,0,1,0},
			{0,1,1,0,1,0,1,0,1,0,1,0,1,1,1,0,1,0,1,0,1,0,1,0},
			{0,0,1,0,1,0,1,0,0,0,0,0,0,0,0,0,1,0,1,0,1,0,1,0},
			{1,0,1,0,0,0,1,1,1,1,1,1,1,0,1,0,1,0,1,0,1,0,1,0},
			{1,0,1,1,1,0,1,0,0,0,0,0,0,0,1,0,1,0,1,0,1,0,1,0},
			{1,0,0,0,0,0,1,0,1,0,1,1,1,0,1,0,1,0,0,0,1,0,0,0},
			{1,0,1,1,1,1,1,0,1,0,1,0,0,0,0,0,1,0,1,0,1,1,1,1},
			{1,0,0,0,0,0,0,0,1,0,1,1,0,1,1,1,1,0,0,0,0,1,0,1},
			{1,1,1,1,1,1,1,0,1,0,1,0,0,0,0,0,1,1,1,1,1,1,0,1},
			{0,0,0,0,0,0,0,0,1,0,1,1,1,1,0,0,0,1,0,0,0,0,0,1},
			{0,1,1,1,1,1,1,1,1,0,0,0,0,0,0,1,0,1,0,1,1,1,1,1},
			{0,0,0,0,1,0,0,0,1,0,1,1,1,1,0,1,0,0,0,0,0,0,0,0},
			{1,0,1,0,0,0,1,0,1,0,0,0,0,0,0,1,1,1,1,1,1,1,1,0}};
		
	public static int size = map.length;
	
	//들린 곳 체크
	public static boolean[][] visit = new boolean[size][size];
	
	//인덱스를 저장하는 큐
	public static Queue<Index> mq = new LinkedList<>();
	
	//너비우선탐색
	public static void bfs(int x, int y) { //시작 행, 열
		Index curr = new Index(x,y);
		map[x][y] = 1; // 첫 위치 visist설정
		
		while(true) {
			if(curr.getX() == size - 1 && curr.getY() == size - 1) { // 골인지점 설정
				System.out.println("미로탈출 완료!");
				break;
			} else {
				findWay(curr); // 현재 위치를 기준으로 길 탐색
				Index temp = mq.poll();
				visit[temp.getX()][temp.getY()] = true; // 이동했으니 true
				System.out.println("" + temp.getX() + " " + temp.getY() + "로 이동");
				curr.setX(temp.getX()); // 현재 위치를 poll으로 변경
				curr.setY(temp.getY());
			}
		}
	}
	
	
	// 현재 위치의 상하좌우 탐색 메서드
	public static void findWay(Index curr) {
		int x = curr.getX();
		int y = curr.getY();
		
		// 위 탐색
		if (x > 0) {
			if (map[x-1][y] != 1) { //벽이 아니면 추가
				mq.offer(new Index(x - 1, y));
				map[x-1][y] = 1; //추가하고 벽으로 만들어버림
			}
		}
		
		// 왼쪽 탐색
		if (y > 0) {
			if (map[x][y-1] != 1) { 
				mq.offer(new Index(x, y-1));
				map[x][y-1] = 1;
			}
		}
		
		// 오른쪽 탐색
		if (y < size-1) {
			if (map[x][y+1] != 1 && !visit[x][y+1]) { 
				mq.offer(new Index(x, y + 1));
				map[x][y+1] = 1;
			}
		}

		// 아래 탐색
		if (x < size-1) {
			if (map[x+1][y] != 1) { 
				mq.offer(new Index(x + 1, y));
				map[x+1][y] = 1;
			}
		}
	}
}

 

class Index

class Index {
	private int x;
	private int y;
	
	public Index() {
	}
	
	public Index(int x, int y) {
		this.x = x;
		this.y = y;
	}
	
	public int getX() {
		return x;
	}
	public void setX(int x) {
		this.x = x;
	}
	public int getY() {
		return y;
	}
	public void setY(int y) {
		this.y = y;
	}
}

。。。