if “1” add a neighborhood ，Perimeter-2.

public class Solution {

public int islandPerimeter(int[][] grid) {

int res=0;

for(int i=0;i<grid.length;i++){

for(int j=0;j<grid[i].length;j++){

if(grid[i][j]==1){

res+=4;

if(j!=0&&grid[i][j-1]==1)

res-=2;

if(i!=0&&grid[i-1][j]==1)

res-=2;

}

```
}
}
return res;
}
```

}