463. Island Perimeter

 1 class Solution {
 2     public int islandPerimeter(int[][] grid) {
 3         if(grid == null) return 0;
 4         int row = grid.length;
 5         if(row == 0) return 0;
 6         int col = grid[0].length;
 7         int res = 0;
 8         for(int i = 0; i < row; i++) {
 9             for(int j = 0; j < col; j++) {
10                 if(grid[i][j] == 1) {
11                     res += 4;
12                     if(i+1 < row && grid[i+1][j] == 1) {
13                         res -= 1;
14                     }
15                     if(i-1 >= 0 && grid[i-1][j] == 1) {
16                         res -= 1;
17                     }
18                     if(j+1 < col && grid[i][j+1] == 1) {
19                         res -= 1;
20                     }
21                     if(j-1 >= 0 && grid[i][j-1] == 1) {
22                         res -= 1;
23                     }
24                 }
25             }
26         }
27         return res;
28         
29     }
30 }