leetcode 463. Island Perimeter

/**
* leetcode 463. Island Perimeter
* @param grid
* @return
* 2017年2月28日下午3:06:42
*/
public int islandPerimeter(int[][] grid) {
int perimeter = 0;
for (int i = 0; i < grid.length; i++) {

for (int j = 0; j < grid[i].length; j++) {
int top = i-1, bottom=i+1, left=j-1, right = j+1;
int val_t = (top<0?1:1-grid[top][j]);
int val_b = (bottom>=grid.length?1:1-grid[bottom][j]);
int val_l = (left<0?1:1-grid[i][left]);
int val_r=(right>=grid[i].length?1:1-grid[i][right]);
if (grid[i][j]==1) {						// is Island
perimeter+=val_t+val_b+val_l+val_r;
}
}
}

return perimeter;
}