Easy solution without dfs, just iterate each cell and count how many edges we need to add : )

```
public int islandPerimeter(int[][] grid) {
int sum = 0;
if (grid == null || grid.length == 0 || grid[0].length == 0) return sum;
for (int i = 0; i < grid.length; i++) {
for (int j = 0; j < grid[0].length; j++) {
if (grid[i][j] == 0)
continue;
if (i == 0 || grid[i-1][j] == 0) sum++;
if (i == grid.length - 1 || grid[i+1][j] == 0) sum++;
if (j == 0 || grid[i][j-1] == 0) sum++;
if (j == grid[0].length - 1 || grid[i][j+1] == 0) sum++;
}
}
return sum;
}
```