JAVA ac代码:

package abcd;
import java.util.*;
import java.util.StringTokenizer;
import java.io.*;

public class Main {
	static int n;
	static int[][] a;//矩阵
	static int ans=0;//答案
	static int[] dx= {0,0,-1,1};
	static int[] dy= {1,-1,0,0};
	public static void main(String[] args) {
		n=in.nextInt();
		a=new int[n][n];
		for(int i=0;i<n;i++) {
			for(int j=0;j<n;j++) {
				a[i][j]=in.nextInt();
			}
		}
    //遍历图
		for(int i=0;i<n;i++) {
			for(int j=0;j<n;j++) {
        //当这个点是陆地
				if(a[i][j]==1) {
					ans++;//岛屿数+1
					bfs(i,j);//将相连的陆地全部设置为0
				}
			}
		}
		
		out.println(ans);
		out.close();
	}

	
	

	private static void bfs(int i, int j) {
			
			Queue<int[]> q=new LinkedList<>();
			q.add(new int[]{i,j});//将当前点入队
			//遍历直到周围都是0
			while(!q.isEmpty()) {
				//获得当前相连陆地点的坐标
				int[] temp=q.poll();
				int x=temp[0];
				int y=temp[1];
				//枚举这个坐标上下左右四个点
				for(int k=0;k<4;k++) {
					int x1=x+dx[k];
					int y1=y+dy[k];
					//越界分析和是海洋
					if(x1<0||y1<0||x1>=n||y1>=n||a[x1][y1]==0)continue;
					q.add(new int[] {x1,y1});
					a[x1][y1]=0;//设置为海洋，不再遍历
				}
			}
		
	}




	static FastReader in=new FastReader();
	static PrintWriter out=new PrintWriter(System.out);
	static class FastReader{
		static BufferedReader br;
		static StringTokenizer st;
		FastReader(){
			br=new BufferedReader(new InputStreamReader(System.in));
		}
		String next() {
			String str="";
			while(st==null||!st.hasMoreElements()) {
				try {
					str=br.readLine();
				}catch(IOException e) {
					throw new RuntimeException(e);
				}
				st=new StringTokenizer(str);
			}
			return st.nextToken();
		}
		int nextInt() {
			return Integer.parseInt(next());
		}
		double nextDouble() {
			return Double.parseDouble(next());
		}
		long nextLong() {
			return Long.parseLong(next());
		}
	}
	
}