[백준][자바][2146 다리] 해결못함

ㅠㅠ..

또 해결못했다 접근 방법은 맞는거 같은데 뭐가 문젠지 찾지못했다...

잠시 쉬었다해야곘다...너무 힘ㅁ들다....

package aa;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.LinkedList;
import java.util.Queue;
import java.util.StringTokenizer;
class b_Point{
	int x; 
	int y;
	b_Point(int y, int x){
		this.x = x;
		this.y = y; 
	}
}
public class backjoon_2146_다리 {
	static int[][] map = new int [101][101];
	static int[][] island = new int [101][101];
	static int[][] temp = new int [101][101];
	static boolean[][] visited = new boolean[101][101];
	static int n;
	static int[] dx = {0,0,-1,1}; 
	static int[] dy = {-1,1,0,0}; 
	static int low = 100;
	static int bridgeCnt = 0;
	static Queue bq = new LinkedList();
	public static void main(String[] args) throws IOException{
		
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		n = Integer.parseInt(br.readLine());
		
		StringTokenizer st;
		for (int i = 0; i < n; i++) {
			st = new StringTokenizer(br.readLine(), " ");
			int idx = 0;
			while(st.hasMoreTokens()) {
				map[i][idx] = Integer.parseInt(st.nextToken());
				idx++;
			}
		}
		
		/*섬마다 번호 매기기 */
		int islandName = 1;
		for(int i =0 ; i < n; i++) {
			for (int j = 0; j < n; j++ ) {
				if(!visited[i][j] && map[i][j] == 1) {
					find_Island(i,j,islandName);
					islandName++;
				}
			}
		}
		//한번썻으니 초기화 
		visited = new boolean[101][101];
		printMap();
		
		//island 마다 bfs 돌리자 
		for (int islandNum = 1; islandNum < islandName; islandNum++) {
			
			//맨 처음 엣지 찾고 큐에 넣기
			for(int i =0 ; i < n; i++) {
				for (int j = 0; j < n; j++ ) {
					if(island[i][j] == islandNum) {
						if(isEdge(i,j)) {
							//System.out.println(i+ " "+ j);
							bq.add(new b_Point(i, j));
						}
					}
				}
			}
			//섬마다 다리 건설 
			while(true) {
				if ( buliding_Bridge(islandNum)) {
					break;
				}
				//printMap();
			
			}
			//초기화 
			restore();	
		}
	
		System.out.println(low - 1 );
		//printMap();
	}
	/* 초기화 하기 */
	public static void restore() {
		//island 초기화
		for(int i =0 ; i < n; i++) {
			for (int j = 0; j < n; j++ ) {
				island[i][j] = temp[i][j];
			}
		}
		//비짓 배열 초기화
		visited = new boolean[101][101];
		bq = new LinkedList();
		bridgeCnt = 0;
	}

	
	/* 제일 끝단 찾기 */
	public static boolean isEdge(int sero, int garo) {
		for(int i = 0; i < 4; i++) {
			int xx = dx[i] + garo;
			int yy = dy[i] + sero;
			if(xx >= 0 && xx < n && yy >= 0 && yy < n) {
				if(island[yy][xx] == 0 ) {
					return true;
				}
			}
		}
		return false;
	}
	
	/*최저점 찾기 */
	public static void find_lowest(int value) {
		if(low > value) {
			low = value;
		}
	}
	
	
	/* 섬마다 bfs로 돌리기  */
	public static boolean buliding_Bridge(int islandNum) {
		bridgeCnt += 1;
		//System.out.println("buliding");
		int bqSize = bq.size();
		for(int size = 0; size < bqSize; size++ ) {
				b_Point b = bq.poll();
				int garo = b.x;
				int sero = b.y;
				for(int i = 0; i < 4; i++) {
					int xx = dx[i] + garo;
					int yy = dy[i] + sero;
					if(xx >= 0 && xx < n && yy >= 0 && yy < n) {
						//방문 안했고 내 섬번호가 아니고,
						if(!visited[yy][xx] && island[yy][xx] != islandNum) {
							 //0이 아니라면( 섬인경우 )
							 if(island[yy][xx] != 0 ) {
								//System.out.println(yy+ "  " + xx);
								find_lowest(bridgeCnt);
								return true;
							}
							else {
								island[yy][xx] = islandNum;
								visited[yy][xx] = true;
								bq.add(new b_Point(yy,xx));
							}
						}
					}
				}
			
		}
		return false;
	}
	/*dfs로 각 섬의 번호 매기기  */
	public static void find_Island(int sero, int garo, int name) {
		visited[sero][garo] = true;
		island[sero][garo] = name;
		temp[sero][garo] = name;
 		for(int i = 0; i < 4; i++) {
			int xx = dx[i] + garo;
			int yy = dy[i] + sero;
			if(xx >=0 && xx < n && yy >= 0 && yy < n) {
				if(!visited[yy][xx] && map[yy][xx] == 1) { 
					visited[yy][xx] = true;
					island[yy][xx] = name;
					temp[yy][xx] = name;
					find_Island(yy,xx,name);
				}
			}
		}
		
	}
	public static void printMap() {
		System.out.println("----");
		for (int i = 0 ; i < n; i++) {
			for(int j = 0; j< n; j++) {
				System.out.print(island[i][j] + " ");
			}
			System.out.println();
		}
		//System.out.println(mwh.Sangun_Point.x);
		//System.out.println(mwh.Sangun_Point.y);
		System.out.println("----");
	}
	
}