Java solution with DFS

• ``````public class Solution {
public int islandPerimeter(int[][] grid) {
if (grid == null) return 0;
for (int i = 0 ; i < grid.length ; i++){
for (int j = 0 ; j < grid[0].length ; j++){
if (grid[i][j] == 1) {
return getPerimeter(grid,i,j);
}
}
}
return 0;
}

public int getPerimeter(int[][] grid, int i, int j){
if (i < 0 || i >= grid.length || j < 0 || j >= grid[0].length) {return 1;}
if (grid[i][j] == 0) {
return 1;
}
if (grid[i][j] == -1) return 0;

int count = 0;
grid[i][j] = -1;

count += getPerimeter(grid, i-1, j);
count += getPerimeter(grid, i, j-1);
count += getPerimeter(grid, i, j+1);
count += getPerimeter(grid, i+1, j);

return count;

}
}
``````

• Good solution, really easy to understand

• Could you please explain this
``if (i < 0 || i >= grid.length || j < 0 || j >= grid[0].length) {return 1;}
if (grid[i][j] == 0) {
return 1;
}
if (grid[i][j] == -1) return 0;"

why the first two if's return 1? the last if return 0?

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