Leet Code 463. Island Perimeter

Example 1:

Input: grid = [[0,1,0,0],[1,1,1,0],[0,1,0,0],[1,1,0,0]]
Output: 16
Explanation: The perimeter is the 16 yellow stripes in the image above.

package pep.Day40;

public class Island_Perimeter {
    public static void main(String[] args) {
        int[][] grid = {{0, 1, 0, 0}, {1, 1, 1, 0}, {0, 1, 0, 0}, {1, 1, 0, 0}};

        System.out.println(islandPerimeter(grid));
    }

    public static int islandPerimeter(int[][] grid) {
        int boxes = 0, nbr = 0;
        int[][] dirns = {{-1, 0}, {0, -1}, {1, 0}, {0, 1}};

        for (int i = 0; i < grid.length; i++) {
            for (int j = 0; j < grid[0].length; j++) {
                if (grid[i][j] == 1) {
                    boxes++;
                    for (int[] dir : dirns) {
                        int x = dir[0] + i;
                        int y = dir[1] + j;

                        if ((x >= 0 && x < grid.length) && (y >= 0 && y < grid[0].length)) {
                            if (grid[x][y] == 1) {
                                nbr++;
                            }
                        }
                    }
                }
            }
        }
        return 4 * boxes - nbr;
    }
}