import java.util.LinkedList;
import java.util.Queue;
public class numIslands200 {
//深度优先算法
public int numIslands(char[][] grid) {
if(grid==null||grid.length==0) return 0;
int r=grid.length;
int l=grid[0].length;
int num_islands=0;
for(int i=0;i=nr||l>=nl||grid[r][l]=='0'){
return;
}
grid[r][l] = '0';
for(int x=0;x list=new LinkedList<>();
list.add(new int[]{i,j});
while(!list.isEmpty()){
int[] cur=list.remove();
i= cur[0];j=cur[1];
if(0 <= i && i < grid.length && 0 <= j && j < grid[0].length && grid[i][j] == '1') {
grid[i][j] = '0';
list.add(new int[] { i + 1, j });
list.add(new int[] { i - 1, j });
list.add(new int[] { i, j + 1 });
list.add(new int[] { i, j - 1 });
}
}
}
}