```
class Solution {
public:
int islandPerimeter(vector<vector<int>>& grid) {
int p = 0;
for (int i = 0; i < grid.size(); ++i)
for (int j = 0; j < grid[i].size(); ++j)
if (grid[i][j] == 1)
p += (i == 0 || grid[i - 1][j] == 0) + (i == grid.size() - 1 || grid[i + 1][j] == 0) +
(j == 0 || grid[i][j - 1] == 0) + (j == grid[i].size() - 1 || grid[i][j + 1] == 0);
return p;
}
};
```