class Solution {

public:

    int islandPerimeter(vector<vector<int>>& grid)

    {

        if (grid.empty() || grid[0].empty())

        {

            return 0;

        }

        int m = grid.size(), n = grid[0].size(), res = 0;

        for (int i = 0; i < m; ++i)

        {

            for (int j = 0; j < n; ++j)

            {

                if (grid[i][j] == 0)

                {

                    continue;

                }

                if (j == 0 || grid[i][j - 1] == 0)

                {

                    ++res;

                }

                if (i == 0 || grid[i - 1][j] == 0)

                {

                    ++res;

                }

                if (j == n - 1 || grid[i][j + 1] == 0)

                {

                    ++res;

                }

                if (i == m - 1 || grid[i + 1][j] == 0)

                {

                    ++res;

                }

            }

        }

        return res;

    }

};