蒟蒻的题解，本题主要思路就是：遍历一遍地图，每次遇到了1就dfs把与他相邻的1以及它本身全都搞成0，同时计数器+1 ，这样遍历完一遍岛屿数量也就出来了！！

//package TemplateQuestion;
import javax.annotation.processing.SupportedSourceVersion;
import java.io.*;
public class Main{ //岛屿的数量   ，看到题目就知道是tmd  DFS了。。.
    static int n;
    static int [][]arr;
    static int count;
    static StreamTokenizer st;
    static PrintWriter pw;
    static int []mx={-1,1,0,0};
    static int []my={0,0,-1,1};
    static void dfs(int a,int b)
    {
        arr[a][b]=0;
      for(int i=0;i<4;i++)
      {
          int tx=a+mx[i];
          int ty=b+my[i];
          if(tx<1||tx>n||ty<1||ty>n||arr[tx][ty]==0)
          {
              continue;
          }
          dfs(tx,ty);
      }
    }
   public static void main(String[] args) throws IOException {
        st=new StreamTokenizer(new BufferedReader(new InputStreamReader(System.in)));
        pw=new PrintWriter(System.out);
        count=0;
        st.nextToken();
        n= (int) st.nval;
        arr=new int[n+1][n+1];
        for(int i=1;i<=n;i++)
        {
            for(int j=1;j<=n;j++)
            {
                st.nextToken();
                arr[i][j]= (int) st.nval;
            }
        }
        for(int i=1;i<=n;i++)
        {
            for(int j=1;j<=n;j++)
            {
                if(arr[i][j]==1)
                {
                    count++;
                    dfs(i,j);
                }
            }
        }
        System.out.println(count);
    }
}